Method of manufacturing a golf ball having one or more layers

ABSTRACT

The present invention relates to golf ball components and golf balls comprising high levels of pre-vulcanized or pre-crosslinked materials, as well as methods of making same. The pre-vulcanized or pre-crosslinked materials are typically thermoset materials that are fragmented or ground into a powder, exposed to high pressure, high temperature sintering (“HPHTS”) and molded into the desired shape.

FIELD OF THE INVENTION

The present invention relates to golf balls containing high levels ofpre-vulcanized or pre-crosslinked materials. The invention alsoencompasses methods of making golf balls that include high levels one ormore pre-vulcanized or pre-crosslinked materials.

BACKGROUND OF THE INVENTION

Golf balls typically contain materials that can be difficult to recycle.In particular, golf balls contain thermoset materials which, like rubberin tires, do not degrade and pose serious threats to the environment. In1844, Charles Goodyear obtained U.S. Pat. No. 3,633 directed to sulfurvulcanization and further stated that “[n]o degree of heat, withoutblaze can melt it . . . It resists the most powerful chemical reagents.”Although Goodyear's sulfur vulcanization provided a significantbreakthrough to the industrial revolution, he also created one of themost difficult materials to recycle. There have been many efforts todevelop methods of recycling and reclaiming rubber, especially in viewof the increasing amount of scrap rubber produced by items, such astires.

However, there is no method to date that utilize high levels ofpre-vulcanized materials in golf balls. Thus, a need exists to producegolf ball components with material properties modified by the use ofhigh levels of pre-vulcanized materials.

SUMMARY OF THE INVENTION

The present invention relates to a golf ball comprising greater thanabout 60 parts of one or more pre-vulcanized or pre-crosslinked materialper 100 parts of base rubber material. In one embodiment, the golf ballcomprises one or more of a core, and cover, wherein the pre-vulcanizedor pre-crosslinked material is disposed in at least a portion of thecore, cover, or a combination thereof. In another embodiment, the golfball comprises one or more of an innermost core, one or moreintermediate layers, and outermost cover, wherein the high levels ofpre-vulcanized or pre-crosslinked material is disposed in at least aportion of the core, intermediate layer, cover, or a combinationthereof.

In one embodiment, the at least one of the cover, the core, and theoptional intermediate layer comprises from about 60 parts to about 200parts of one or more pre-vulcanized or pre-crosslinked material per 100parts of base rubber. In another embodiment, the at least one of thecover, the core, and the optional intermediate layer comprises fromabout 70 parts to about 150 parts of one or more pre-vulcanized orpre-crosslinked material per 100 parts of base rubber.

In one embodiment, the pre-vulcanized or pre-crosslinked material isre-crosslinked by high pressure, high temperature sintering (“HPHTS”),and the pre-vulcanized or pre-crosslinked material is a thermosetmaterial. In another embodiment, the thermoset material is selected fromthe group consisting of a thermoset natural or synthetic rubber,thermoset polyurethane, thermoset polyurea, thermoset polyolefin,thermoset phenol-formaldehyde resin, thermoset amino resin, thermosetfuran resin, thermoset unsaturated polyester resin, thermoset vinylester resin, thermoset cyanate esters, thermoset acrylic resins,thermoset epoxy resin, thermoset silicones, thermoset polyimides, andmixtures thereof. In yet another embodiment, thermoset material isselected from the group consisting of styrene butadiene; polybutadiene;isoprene; polyisoprene; trans-isoprene; ethylene propylenediene rubber;fluoroelastomer; silicone rubber; epoxy rubber; nadimide-, cyanate- ormaleimide-terminated thermosetting polyimides; and mixtures thereof.

In one embodiment, the pre-vulcanized or pre-crosslinked materialfurther comprises a cis-to-trans catalyst and free radical source; acrosslinking agent; a vulcanization accelerator; an anti-reversionagent, or a mixture thereof. In another embodiment, the anti-reversionagent is 1,3-bis-(citraconimidomethyl)benzene,hexamethylene-1,6-bis(thiosulfate), or a mixture thereof.

In one embodiment, the golf ball has an Atti compression of at leastabout 40, a coefficient of restitution of at least about 0.7, preferablyat least about 0.78. In another embodiment, the golf ball has an initialvelocity of about 245 ft/s or greater and in yet another embodiment, thegolf ball has an initial velocity of about 253 ft/s to about 254 ft/s.

In one embodiment, the golf ball has a ball spin rate of about 1200 rpmto about 4000 rpm when the golf ball is hit with a golf driver, and thegolf ball has a ball spin rate of about 6500 rpm to about 10,000 rpmwhen the golf ball is struck with an 8-iron.

In one embodiment, the flexural modulus of the intermediate layer isfrom about 500 psi to about 500,000 psi and the flexural modulus of thecover is from about 500 psi to about 150,000 psi. In another embodiment,the core has a hardness of about 20 Shore C to about 80 Shore D, theintermediate layer has a hardness of about 30 Shore D or greater, andthe cover has a hardness of about 20 Shore A to about 70 Shore D. In yetanother embodiment, the golf ball further comprises a filler comprisingat least one density adjusting filler. In another embodiment, thedensity adjusting filler is a metal powder or metal oxide.

The present invention also encompasses a method of manufacturing a golfball comprising the steps of providing a core, optionally providing oneor more intermediate layers disposed outside the core; and providing atleast one cover over the core and optional intermediate layer, whereinat least one of the cover, the core, and the optional intermediate layercomprises greater than about 60 parts of one or more pre-vulcanized orpre-crosslinked material per 100 parts of base rubber material. Themethod includes manufacturing golf balls having the characteristicsand/or materials as described above.

The present invention also encompasses a method of forming a golf ballcomponent comprising the steps of providing greater than about 60 partsof one or more pre-vulcanized or pre-crosslinked material per 100 partsof base rubber material and fragmenting, cutting, grinding or shreddingthe pre-vulcanized or pre-crosslinked materials into a powder; filling amold with said powder; and applying high pressure and high temperaturesintering for a period of time sufficient to re-crosslink thepre-vulcanized or pre-crosslinked materials and forming a re-crosslinkedproduct; wherein the golf ball component is a cover, cover layer,intermediate layer, core, or core layer. The method includesmanufacturing golf balls having the characteristics and/or materials asdescribed above.

In one embodiment, the powder has a particle size from about 5 μm toabout 10000 μm. In yet another embodiment, the mold has an inner cavitythat has a substantially ellipsoid, cylindrical, prismatic or cup shape.In one embodiment, the mold cavity is coated with a layer of anti-sticksubstance or low friction coating. In another embodiment, the moldfurther comprises a piston.

In one embodiment, the pressure is from about 50 psi to about 5,000 psi.In another embodiment, the temperature is from about 80° C. to about300° C. In yet another embodiment, the sintering time is from about 1minute to about 24 hours.

In one embodiment, the re-crosslinked product is in the shape of asphere having a diameter from about 0.090 inches to about 1.650 inches.In another embodiment, the re-crosslinked product is in the shape of ahemispherical shell having an outer radius from about 0.045 inches toabout 0.900. In yet another embodiment, the hemispherical shell has athickness from about 0.001 inches to 0.500 inches. In anotherembodiment, the re-crosslinked product is in the shape of adimpled-sphere having a diameter of from about 1.620 inches to about1.800 inches, preferably about 1.68 inches.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to golf balls including high levels of oneor more pre-vulcanized or pre-crosslinked materials. In particular, thepresent invention encompasses the use of high levels of pre-vulcanizedor pre-crosslinked materials, including waste materials formed from themanufacture of golf balls, and forming new golf ball componentstherefrom. The invention also encompasses methods of making golf ballsthat include high levels of one or more pre-vulcanized orpre-crosslinked materials. In particular, high-pressure, hightemperature sintering (“HPHTS”) is utilized to fuse and re-crosslinkfinely ground pre-vulcanized or pre-crosslinked materials intore-crosslinked products that are virtually indistinguishable from theoriginal products in terms of performance.

As used herein, the phrase “high levels of one or more pre-vulcanized orpre-crosslinked materials” includes compositions comprising greater thanabout 60 parts by weight per 100 parts of base rubber. In oneembodiment, the one or more pre-vulcanized or pre-crosslinked materialsis present in between about 60 parts to about 200 parts by weight per100 parts of base rubber. In another embodiment, the one or morepre-vulcanized or pre-crosslinked materials is present in between about70 parts to about 150 parts by weight per 100 parts of base rubber. Inyet another embodiment, the one or more pre-vulcanized orpre-crosslinked materials is present in between about 75 parts to about125 parts by weight per 100 parts of base rubber. The upper and lowerlimits of the ranges disclosed herein are interchangeable to form newranges. For example, the amount of the one or more pre-vulcanized orpre-crosslinked materials may be present between about 60 parts to about75 parts by weight per 100 parts of base rubber, or between about 75parts to about 200 parts by weight per 100 parts of base rubber.

“Pre-vulcanized” materials include sulfur-based chemical compounds thatalready have been vulcanized, in particular, polymer chains joinedtogether (i.e., crosslinked) by sulfur-sulfur bridges to give a threedimensional polymeric network. “Pre-crosslinked” materials includechemical compounds that already have been crosslinked, in particular,polymer chains that are joined together or crosslinked by peroxides orfree radicals. Typically, pre-crosslinked materials contain polymerchains are joined together by chemical bridges that are notsulfur-sulfur bridges. For example, the polymer chains can containperoxide moieties and/or free radicals that react with other peroxidemoieties and/or free radicals of other polymer chains to formcrosslinked material. In another example, peroxides, free radicalsand/or free radical-generators are contacted with the polymer chains tofacilitate crosslinking between polymer chains.

The pre-vulcanized or pre-crosslinked materials of the present inventionmay be used in any type of ball construction. For example, the ball mayhave a one-piece, two-piece, or three-piece design, a multi-layer core,a multi-layer cover, one or more intermediate layers. As used herein,the term “multi-layer” means at least two layers. For example, there-crosslinked products may be used in a core, intermediate layer,and/or cover of a golf ball, each of which may have a single layer ormultiple layers. Thus, the invention encompasses golf balls thatcomprises at least one layer formed from pre-vulcanized orpre-crosslinked material. As used herein, the term “layer” includes anygenerally spherical portion of a golf ball, i.e., a golf ball core orcenter, an intermediate layer, and or a golf ball cover.

In one embodiment, a golf ball core includes high levels ofpre-vulcanized or pre-crosslinked material. In another embodiment, agolf ball having more than one layer in the core includes in at leastone of the core layers high levels of pre-vulcanized or pre-crosslinkedmaterial.

In another embodiment, a golf ball intermediate layer includes highlevels of pre-vulcanized or pre-crosslinked material. In anotherembodiment, a golf ball having more than one intermediate layer includesin at least one of the intermediate layers high levels of pre-vulcanizedor pre-crosslinked material.

In yet another embodiment, a golf ball cover includes high levels ofpre-vulcanized or pre-crosslinked material. In another embodiment, agolf ball having more than one cover includes in at least one of thecover layers high levels of pre-vulcanized or pre-crosslinked material.

The present invention encompasses golf balls made substantially orentirely from pre-vulcanized or pre-crosslinked material. In particular,the core, intermediate layer, if present, and/or cover may besubstantially or completely formed from finely ground pre-vulcanized orpre-crosslinked material that has been re-crosslinked by HPHTS. In oneembodiment of the invention, the core, intermediate layer, if present,and/or cover may consist essentially of pre-vulcanized orpre-crosslinked material.

The present invention also encompasses golf balls in which a portion ofthe golf balls are formed from high levels of pre-vulcanized orpre-crosslinked material. Thus in one embodiment, the core, intermediatelayer, if present, and/or cover comprises from about 37.5 weight percentto about 100 weight percent of pre-vulcanized or pre-crosslinkedmaterial, preferably from about 40 weight percent to about 70 weightpercent of pre-vulcanized or pre-crosslinked material, more preferablyfrom about 45 weight percent to about 60 weight percent ofpre-vulcanized or pre-crosslinked material. In embodiments where golfball components (i.e., core(s), intermediate layer(s) or cover(s)) arenot comprised of high levels of pre-vulcanized or pre-crosslinkedmaterial, conventional materials typically used to form such componentsmay be utilized.

In addition to forming a component of a golf ball, such as a core,intermediate layer, or cover layer, substantially or entirely frompre-vulcanized or pre-crosslinked material, the golf ball may also havea 1-piece construction. The material used to form a 1-piece ball maycomprise similar amounts of pre-vulcanized or pre-crosslinked materialas described in any other embodiment described herein. For instance, the1-piece ball may be formed of a material consisting essentially ofpre-vulcanized or pre-crosslinked material. Likewise, the 1-piece ballmay be formed of a material comprising varying amounts of pre-vulcanizedor pre-crosslinked material by weight percent as described above andelsewhere herein. Once formed, the 1-piece ball may be painted to adesired color, such as white, and/or may be coated with a UV coating,scuff-resistant coating, or the like.

Pre-vulcanized or pre-crosslinked materials include any thermosetmaterial that already has been cured or crosslinked. Such materials areknown to one of ordinary skill in the art and include, but are notlimited to, cured or crosslinked golf ball material, rubber fromrubber-containing commercial and industrial products (e.g., tires,fabrics, garments, footwear, scrap rubber and the like), or mixturesthereof. Preferably, the pre-vulcanized or pre-crosslinked materialscomprise cured or crosslinked golf ball material. In particular, suchpre-vulcanized or pre-crosslinked golf ball material may originate froman already-manufactured golf ball, or from waste or excess materialsproduced in the golf ball manufacturing process (including swarf andregrind material). In addition, the use of pre-vulcanized powderedrubber, such as those disclosed in U.S. Pat. No. 6,423,760, which isincorporated herein by reference in its entirety, is encompassed by thepresent invention.

In one embodiment, pre-vulcanized or pre-crosslinked golf ball materialoriginating from one golf ball component may be used to make are-crosslinked product for the same component. For example,pre-vulcanized or pre-crosslinked golf ball material from the core maybe finely ground and re-crosslinked using HPHTS to form a new materialfor use in a new golf ball core. Likewise, pre-vulcanized orpre-crosslinked golf ball material from a cover may be subject to HPHTSto make re-crosslinked product for a new cover, and cured or crosslinkedgolf ball material from an intermediate layer may be subject to HPHTS tomake re-crosslinked product for a new intermediate layer.

In another embodiment, pre-vulcanized or pre-crosslinked golf ballmaterial originating from one golf ball component may be used to make are-crosslinked product for a different golf ball component. For example,pre-vulcanized or pre-crosslinked golf ball material from the core maybe finely ground and re-crosslinked using HPHTS to form a newintermediate layer or cover. Pre-vulcanized or pre-crosslinked golf ballmaterial from the intermediate layer may be finely ground andre-crosslinked using HPHTS to form a new core or cover; andpre-vulcanized or pre-crosslinked golf ball material from the cover maybe re-crosslinked using HPHTS to form a new core or intermediate layer.

In one embodiment, the pre-vulcanized or pre-crosslinked materialcomprises any pre-vulcanized or pre-crosslinked thermoset material,which includes, but is not limited to, thermoset natural or syntheticrubber, thermoset polyurethane, thermoset polyurea, thermosetpolyolefin, thermoset phenol-formaldehyde resin, thermoset amino resin,thermoset furan resin, thermoset unsaturated polyester resin, thermosetvinyl ester resin, thermoset cyanate esters, thermoset acrylic resins,thermoset epoxy resin, thermoset silicones, thermoset polyimides, ormixtures thereof. In particular, the pre-vulcanized or pre-crosslinkedthermoset material includes, but is not limited to, styrene butadiene;polybutadiene, including cis-polybutadiene, trans-polybutadiene, andblends thereof, as well as cis-to-trans converted polybutadiene;isoprene; polyisoprene; trans-isoprene (including Balata); ethylenepropylenediene rubber; fluoroelastomer; silicone rubber; epoxy rubber;nadimide-, cyanate- or maleimide-terminated thermosetting polyimides; ormixtures thereof.

Preferably, the pre-vulcanized or pre-crosslinked material is extremelyresilient and durable in order to compensate for any loss in thephysical properties that may occur in forming the new re-crosslinkedmaterial. Thus, the present invention encompasses the use ofpre-vulcanized or pre-crosslinked material that comprises a resilientpolymer component, such as polybutadiene. Examples of polybutadieneinclude BUNA® CB22 and BUNA® CB23, commercially available from Bayer ofAkron, Ohio; UBEPOL® 360L and UBEPOL® 150L, commercially available fromUBE Industries of Tokyo, Japan; and CARIFLEX® BCP820 and CARIFLEX®BCP824, commercially available from Shell of Houston, Tex. In oneembodiment, the polybutadiene also can be mixed with other elastomersknown in the art such as natural rubber, polyisoprene rubber and/orstyrene-butadiene rubber in order to modify the properties of thepre-vulcanized or pre-crosslinked material. The polybutadiene typicallyhas a molecular weight of greater than about 200,000. Preferably, thepolybutadiene molecular weight is greater than about 250,000, morepreferably between about 300,000 and 500,000.

In another embodiment, the pre-vulcanized or pre-crosslinked materialfurther comprises a cis-to-trans catalyst. Without being bound by anyparticular theory, it is believed that the cis-to-trans catalystcomponent, in conjunction with a free radical source, acts to convert apercentage of the polybutadiene from the cis- to the trans-conformation.As used herein, “cis-to-trans catalyst” means any component or acombination thereof that will convert at least a portion of cis-isomerto trans-isomer at a given temperature. The cis-to-trans catalystcomponent may include one or more cis-to-trans catalysts describedherein, but typically includes at least one organosulfur component(including metal-containing and nonmetal-containing organosulfurcompounds), a Group VIA component, an inorganic sulfide, a substitutedor unsubstituted aromatic organic compound that does not contain sulfuror metal, an aromatic organometallic compound, or any combinationthereof. Examples of cis-to-trans catalysts are disclosed in, forexample, U.S. Pat. Nos. 6,417,278, 6,291,592, 6,458,895 and 6,162,135,the entirety of which are incorporated herein by reference.

In one embodiment, the cis-to-trans catalyst is a blend of anorganosulfur component and an inorganic sulfide component or a Group VIAcomponent. In another embodiment, the cis-to-trans catalyst is a blendof an organosulfur component, an inorganic sulfide component, and aGroup VIA component.

The cis-to-trans catalyst is typically present in an amount sufficientto produce a reaction product so as to increase the trans-polybutadieneisomer content to contain from about 5 percent to 70 percenttrans-isomer polybutadiene based on the total resilient polymercomponent. The cis-to-trans catalyst is preferably present in an amountfrom about 0.1 pph to 25 pph of the total amount of polybutadiene.

As mentioned above, the cis-to-trans catalyst is utilized in conjunctionwith a free radical. The free-radical source is typically a peroxide,and preferably an organic peroxide, which decomposes during the curecycle. Suitable free-radical sources include organic peroxide compounds,such as di-tert-amyl peroxide, di(2-tert-butyl-peroxyisopropyl)benzeneperoxide or α,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy)3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and the like, and any mixturethereof.

Other examples include, but are not limited to, VAROX® 231XL and VAROX®DCP-R, commercially available from Atofina Chemicals, Inc. of King ofPrussia, Pa.; PERKODOX® BC and PERKODOX®, commercially available fromAkzo Nobel of Chicago, Ill.; and ELASTOCHEM® DCP-70, commerciallyavailable from Rhein Chemie of Trenton, N.J.

It is well known that peroxides are available in a variety of formshaving different activity. The activity is typically defined by the“active oxygen content.” For example, PERKODOX® BC peroxide is 98percent active and has an active oxygen content of 5.8 percent, whereasPERKODOX® DCP-70 is 70 percent active and has an active oxygen contentof 4.18 percent.

The peroxide may be present in an amount greater than about 0.1 pph ofthe total resilient polymer component, preferably about 0.1 pph to about15 pph of the resilient polymer component.

The pre-vulcanized or pre-crosslinked material may also include acrosslinking agent, including one or more metallic salts of unsaturatedfatty acids having 3 to 8 carbon atoms, such as acrylic or methacrylicacid, or monocarboxylic acids, including zinc, calcium, or magnesiumacrylate salts, and the like, and mixtures thereof. Exemplarycrosslinkers include, but are not limited to, one or more metal saltdiacrylates, dimethacrylates, and monomethacrylates, wherein the metalis magnesium, calcium, zinc, aluminum, sodium, lithium, or nickel.Preferred acrylates include zinc acrylate, zinc diacrylate, zincmethacrylate, zinc dimethacrylate, and mixtures thereof. In oneembodiment, zinc methacrylate is used in combination with the zinc saltof pentachlorothiophenol.

The presence of one or more of a cis-to-trans catalyst, free radical, orcrosslinking agent affects the properties of the pre-vulcanized orpre-crosslinked material and may be a factor in the re-crosslinking thatoccurs during HPHTS. Thus, the absence or presence of these additionalcomponents in pre-vulcanized or pre-crosslinked material will be afactor in determining the HPHTS conditions, such as the pressure,temperature and/or time.

Another aspect of the present invention encompasses a method ofpreparing golf ball components that comprises high levels ofpre-vulcanized or pre-crosslinked material. Thus one embodiment includesa method of manufacturing golf balls comprising:

providing a core;

optionally providing one or more intermediate layers disposed outsidethe core; and

providing at least one cover over the core and optional intermediatelayer,

wherein at least one of the cover, the core, and the optionalintermediate layer comprises high levels of pre-vulcanized orpre-crosslinked material.

In one embodiment, the pre-vulcanized or pre-crosslinked material is afinely ground powder that is subjected to high pressure,high-temperature sintering (HPHTS) to form a new re-crosslinked materialfor use as a golf ball component. In another embodiment, high pressureinitially is applied followed by applying high temperature whilemaintaining the high pressure. In yet another embodiment, high pressureand high temperature are applied concurrently.

High-pressure, high-temperature sintering is utilized to re-crosslinkthe pre-vulcanized or pre-crosslinked material, preferably in finelyground form. Without being bound to any theory, it is believed that thepressure applied to compress the particle interfaces into intimatecontact, while the temperature adds the energy needed to break thecrosslink bonds. Subsequently, chemical exchange reactions can occur atthe particle interface and within the particles, thereby fusing orsintering the particles in to a single piece. In particular, theinter-particle and intra-particle chemical reaction is the reforming ofbroken crosslinks, which results in mechanical integrity of the newlyformed rubber part or item.

In one embodiment, the HPHTS includes the steps of providingpre-vulcanized or pre-crosslinked material that is in fragmented orfinely ground particle form, applying a pressure sufficient to compressthe particle interfaces into intimate contact followed by applying atemperature sufficient to re-crosslink the pre-vulcanized orpre-crosslinked material.

In another embodiment, the HPHTS of pre-vulcanized or pre-crosslinkedmaterial is carried out in a mold. The mold shape may be designed sothat the final re-crosslinked product is molded into its final shapeafter being subject to HPHTS. The mold shape also may be designed sothat the re-crosslinked product is in an intermediate shape or form,which requires one or more subsequent steps to shape the re-crosslinkedproduct into final form, i.e., form re-crosslinked product into thedesired golf ball component.

The inner cavity of the mold may have any desired shape. Typically, theinner cavity of the mold has a substantially ellipsoid, cylindrical,prismatic or cup shape. As used herein, the term “prismatic” includesshapes where the bases or ends have the same size and shape and areparallel to one another, and each of whose sides is a parallelogram.Prismatic shapes include box shapes of all types, including cubes andrectangular boxes. In addition, the mold shapes may have minorvariations, for example, a prismatic or rectangular cavity can haverounded edges on at least one of its edges.

If desired, the inside of a mold cavity can be coated with a layer ofmaterial that is an anti-stick substance or low friction coating, suchas TEFLON, silicone spray, or grease, before the mold is filled withfinely ground pre-vulcanized or pre-crosslinked material. Alternativelyand additionally, the interior surfaces of the mold can be made of apolished or smooth metal, such as stainless steel. Any of the abovemethods, as well as methods well-known to one of ordinary skill in theart, may be used to minimize sticking of the shaped articles to themold, facilitating easy removal of the article from the mold.

In one embodiment, the mold includes at least one piston that appliespressure to the pre-vulcanized or pre-crosslinked material. The pistonface may be any shape, but preferably is at least a portion of the shapeof the mold. For example, a mold having an ellipsoid inner cavity shapecan have a piston having a cup-shaped face. Upon applying pressure tothe pre-vulcanized or pre-crosslinked material that is filled to the topof the mold, the resulting re-crosslinked product has a substantiallyspherical shape. In another embodiment, the inner cavity of the mold isa rectangular prism having round edges on the side opposite the pistonand the piston face has an equal cross-sectional area. Upon applyingpressure to the pre-vulcanized or pre-crosslinked material that isfilled to the top of the mold, the resulting re-crosslinked product hasa substantially cubic shape having rounded edges on the side opposed tothe piston, which further can be rounded through traditional means tocreate, for example, a finished core or center for a golf ball.

In one embodiment, a core or center for a golf ball is prepared using anellipsoid mold that is filled to the top with pre-vulcanized orpre-crosslinked material, applying HPHTS sufficient to re-crosslink thepre-vulcanized or pre-crosslinked material and forming a re-crosslinkedproduct that is a finished, spherical core.

In another embodiment, a core layer, intermediate layer, cover layer orcover is prepared using a cup shaped mold that is filled to the top withpre-vulcanized or pre-crosslinked material, applying HPHTS sufficient tore-crosslink the pre-vulcanized or pre-crosslinked material and forminga re-crosslinked product that is a hemispherical shell, two of which maysubsequently be compression molded to form a core layer, intermediatelayer, cover layer or cover.

Prior to loading into a mold, pre-vulcanized or pre-crosslinkedmaterials can be loaded into a cutting, grinding or shredding machine toconvert the materials into smaller fragments. If desired, the cuttingprocess can be done in multiple stages. For example, a first cutting orshredding step can be used to cut the materials into sections or strips,or to shred the materials into large chunks having diameters in therange of about 1 inch to about 20 inches or more. One or more subsequentsteps can follow where the sections, strips or chunks are shredded orground into smaller fragments. Using appropriate cutting, shredding, orgrinding steps coupled with sorting devices (which typically can involvesifting the fragments through specific-sized mesh screens or panels),the pre-vulcanized or pre-crosslinked materials can be reduced tofragments or finely ground powder having any desired size range.

In one embodiment, the pre-vulcanized or pre-crosslinked material isfragmented or finely ground into powder having a particle size fromabout 5 μm to about 10000 μm. In another embodiment, the pre-vulcanizedor pre-crosslinked material has a particle size from about 20 μm toabout 1000 μm. In yet another embodiment, the pre-vulcanized orpre-crosslinked material have a particle size from about 40 μm to about500 μm. In another embodiment, the pre-vulcanized or pre-crosslinkedmaterial has a particle size from about 100 μm to about 250 μm. Asmentioned earlier, the upper and lower limits of the ranges disclosedherein may be freely interchanged to form other new ranges that are alsocontemplated by the present invention. For example, the pre-vulcanizedor pre-crosslinked material has a particle size from about 5 μm to about500 μm in one embodiment, from about 20 μm to about 100 μm in anotherembodiment, and from about 250 μm to about 1000 μm in yet anotherembodiment. This interchangeability of upper and lower limits apply toall ranges disclosed in the invention.

In another embodiment, the pre-vulcanized or pre-crosslinked materialmay have a particle size distribution. Typically, sieves are used toprovide the pre-vulcanized or pre-crosslinked material having particularparticle size distributions. For example, the pre-vulcanized orpre-crosslinked material may be sieved using a vibrating standard sieve.A sieve having utilizing a +60 mesh provides the pre-vulcanized orpre-crosslinked material having particles sizes of greater than 250 μm;a sieve having −60 mesh to +140 mesh provides pre-vulcanized orpre-crosslinked material having particle sizes from about 100 μm toabout 250 μm; and a sieve having −140 mesh to +320 mesh providespre-vulcanized or pre-crosslinked material having particle sizes fromabout 40 μm to about 100 μm.

The pressure serves several purposes, including, inter alia, ensuringthat the entire mold cavity is filled, eliminating or minimizingundesired voids and air pockets that can result when the finely groundpre-vulcanized or pre-crosslinked material is poured into a mold; andreducing the porosity and permeability of the resulting article, makingit more solid and durable. The pressure applied to the pre-vulcanized orpre-crosslinked material during HPHTS is typically greater than 50 psi,greater than 500 psi, or even greater than 1000 psi. In one embodiment,the pressure applied to the pre-vulcanized or pre-crosslinked materialduring HPHTS is from about 50 psi to about 5,000 psi. In anotherembodiment, the applied pressure is from about 200 psi to about 2,500psi. In yet another embodiment, the applied pressure is from about 500psi to about 1,500 psi. As mentioned earlier, the upper and lower limitsof the ranges may be interchanged. For example, the present inventionencompasses applied pressures of from about 50 psi to about 200 psi;from about 1,500 psi to about 5,000 psi; and from about 500 psi to about5,000 psi.

The temperature applied to the pre-vulcanized or pre-crosslinkedmaterial during HPHTS varies depending on the material used. Animportant criteria in determining an appropriate temperature for HPHTSis consideration of the temperature at which onset of chemical stressrelaxation/interchange chemistry of the crosslinking system. As usedherein, the phrase “chemical stress relaxation” refers to the mechanicalrelaxation of stresses caused by the exchanging chemical bonds in anetwork. Both intermittent and continuous chemical stress relaxationyield information about the crosslink network, which undergoes changesat elevated temperatures. These techniques can be used to measure thedestruction of the original network, as well as the formation of the newnetwork at elevated temperatures.

The present invention encompasses methods that utilize HPHTS onpre-vulcanized or pre-crosslinked material having not only sulfurcrosslinked systems, but also for radiation- and peroxide-cured rubbers.The present invention further encompasses the use of pre-vulcanized orpre-crosslinked materials having crosslinked systems having variouscrosslink densities and even polymers that are glasses at roomtemperature.

Typically, the applied temperature is greater than about 70° C. In oneembodiment, the applied temperature is from about 80° C. to about 300°C. In another embodiment, the applied temperature is from about 120° C.to about 260° C. In yet another embodiment, the applied temperature isfrom about 140° C. to about 200° C. and in another embodiment, theapplied temperature is from about 180° C. to about 240° C. The appliedtemperature may be selected based on the type of pre-vulcanized orpre-crosslinked material in order to optimize HPHTS conditions and isreadily ascertainable by one of ordinary skill in the art without undueexperimentation. For example, pre-vulcanized or pre-crosslinked materialsuch as a polysulfide material involves HPHTS temperatures from 130° C.to about 150° C. (applied at about 1160 psi for 1 hour) for sufficientre-crosslinking. In another example, natural rubber involves HPHTStemperatures from about 170° C. to about 190° C. (applied at about 1160psi for 1 hour) for sufficient re-crosslinking. In yet another example,styrene-butadiene rubber involves HPHTS temperatures from about 230° C.to about 250° C. (applied at about 1160 psi for 1 hour).

The sintering time that the high pressure and high temperature isapplied varies from about 1 minute to about 24 hours. In one embodiment,the high pressure and high temperature is applied for about 20 minutesto about 12 hours. In another embodiment, the high pressure and hightemperature is applied for about 30 minutes to about 4 hours. In yetanother embodiment, the high pressure and high temperature is appliedfor about 1 hour to about 2 hours. As mentioned above, the upper andlower limits of the ranges can be interchanged to form new ranges thatare also contemplated in the present invention.

The modulus of the material yields information of the crosslink densityof the overall network. In particular, the relative modulus providesinformation regarding the number of chemical bonds ruptured in view ofthe number of reformed chemical bonds as a result of HPHTS. Thus, arelative modulus having a value of 1 correlates to the formation of onebond for every bond that breaks, i.e., constant crosslink density. Forexample, polysulfide rubber (i.e., Thiokol rubber) has a relativemodulus of 1. A relative modulus having a value of less than onecorrelates to reversion back to an un-crosslinked material, in whichcrosslinks are broken faster than they are reforming. For example,natural rubber has a relative modulus of less than 1. A relative modulusof greater than 1 correlates to forming new crosslinks faster than theyare breaking. For example, styrene-butadiene rubber has a relativemodulus of greater than 1. Most materials are formulated to yield themaximum obtainable strength, which will decrease by either increasing ordecreasing the total crosslink density, corresponding to over-cure andreversion respectively.

Generally, materials having a relative modulus equal to 1 that aresubject to HPHTS to form a re-crosslinked product should recover 100% ofthe properties of the original material. As used herein, the phrase“original material” refers to the pre-vulcanized or pre-crosslinkedmaterial prior to being subject to HPHTS. Such properties includeflexural modulus, tensile strength, tear strength, rebound resilience,abrasion resistance, compression, hardness, crosslink density, andstrength and strain to break. Materials having a relative modulus ofgreater than 1 (over-cure) or less than 1 (reversion) that are subjectto HPHTS have a change in network structure and thus do not recover 100%of the properties of the original material. However, the re-crosslinkedproduct should recover at least no less than about 60% of the propertiesof the original material. In another embodiment, the re-crosslinkedproduct recovers at least about 75% of the properties of the originalmaterial. In yet another embodiment, the re-crosslinked materialrecovers at least about 80% of the properties of the original material.In another embodiment, the re-crosslinked material recovers at leastabout 90% of the properties of the original material.

In one embodiment, additional ingredients may be added to the fragmentedor finely ground pre-vulcanized or pre-crosslinked material prior toHPHTS in order to promote adhesion and crosslinking of the particles.These ingredients include, but are not limited to, crosslinking agents,vulcanization accelerators, anti-reversion agents and the like, as wellas mixtures thereof. In one embodiment, the additional ingredientsinclude, but are not limited to, peroxides, sulfur and sulfur-containingcompounds, zinc pentachlorothiophenol (“ZnPCTP”), acrylates,diacrylates, diisocyanates, urethane prepolymer and the like. Preferredacrylates and diacrylates include metallic salts of unsaturated fattyacids having 3 to 8 carbon atoms, including diacrylates, dimethacrylatesand monomethacrylates, wherein the metal is magnesium, zinc, aluminum,sodium, lithium or nickel. Preferred anti-reversion agents include, butare not limited to, 1,3-bis-(citraconimidomethyl)benzene (PERKALINK 900available from Flexsys of Akron, Ohio),hexamethylene-1,6-bis(thiosulfate) (DURALINK available from Flexsys).

In one embodiment, the additional ingredients are present from about 0.1to about 50 percent by weight of pre-vulcanized or pre-crosslinkedmaterial. In another embodiment, the additional ingredients are presentfrom about 1 to about 20 percent by weight of pre-vulcanized orpre-crosslinked material. In yet another embodiment, the additionalingredients are present from about 3 to about 10 percent by weight ofpre-vulcanized or pre-crosslinked material.

In another embodiment, the golf ball component can be formed using atwo-step process. In particular, the first step involves providing highlevels of pre-vulcanized or pre-crosslinked material, compressing thepre-vulcanized or pre-crosslinked material at moderately high pressures(e.g., from about 250 psi to about 500 psi) and reduced temperature(less than about 180° C.) to form a prep. Square, rectangular orcylindrical preps can be formed with sufficient fusion of particles, asdescribed above, for ease of handling, but preps require additionalpressure and/or temperature to form a re-crosslinked product into itsfinal shape, such as a spherical core component. In another embodiment,the prep is formed into the shape of a cup, which can be later processedinto a core layer, intermediate layer, cover layer or cover.

Core

The invention encompasses the use of high levels of pre-vulcanized orpre-crosslinked material in a one-piece core or a multi-layer core. Thusin one embodiment, a core includes high levels of pre-vulcanized orpre-crosslinked material that has been re-crosslinked by HPHTS. Inanother embodiment, the core includes high levels of a blend ofpre-vulcanized or pre-crosslinked material that has been re-crosslinkedby HPHTS and one or more conventional core material described below. Inthis embodiment, the core may be formed by providing high levels ofpre-vulcanized or pre-crosslinked material and uncured conventional corematerial, and subjecting the blend to HPHTS that will simultaneouslyre-crosslink the pre-vulcanized or pre-crosslinked material and cure theuncured conventional core material.

As used herein, the term “core” means the innermost portion of a golfball, and may include one or more layers. When a multi-layer core iscontemplated, the core is the innermost component with one or moreadditional core layers disposed thereon. At least a portion of the core,typically the center, is solid, semi-solid, hollow, powder-filled orfluid-filled. As used herein, the term “fluid” means a gas, liquid, gel,paste, or the like, or a combination thereof.

Golf balls having a one-piece core or any portion of a multi-layer corethat is not formed from high levels of pre-vulcanized or pre-crosslinkedmaterial may be formed from any core material suitable for use in golfballs that is known to one of ordinary skill in the art, as discussedbelow. Suitable core materials include thermoset materials, such asrubber, styrene butadiene, polybutadiene, including cis-polybutadiene,trans-polybutadiene, and blends thereof, as well as cis-to-transconverted polybutadiene, isoprene, polyisoprene, trans-isoprene, as wellas thermoplastics, such as ionomer resins, polyamides or polyesters, andthermoplastic and thermoset polyurethane elastomers, and any mixturethereof. In addition, suitable core materials include polyureacompositions.

In some embodiments of the invention, a core that is not entirely formedfrom high levels of pre-vulcanized or pre-crosslinked material may alsoinclude other conventional materials, such as compositions including abase rubber, a crosslinking agent, or a density adjusting filler. Thebase rubber may include natural or synthetic rubbers, as well as anycombination thereof. In one embodiment, the base rubber is1,4-polybutadiene having a cis-structure of at least about 40 percent,of which natural rubber, polyisoprene rubber and/or styrene-butadienerubber may be added thereto. The core may also include one or morecis-to-trans catalyst and a free radical source, as well as acis-to-trans catalyst accelerator and crosslinking agent, as describedabove.

The core may also include a filler. Fillers added to one or moreportions of the golf ball typically include processing aids or compoundsto affect Theological and mixing properties, the specific gravity (i.e.,density-modifying fillers), the modulus, the tear strength,reinforcement, and the like. The fillers are generally inorganic, andsuitable fillers include numerous metals (including metal powders) ormetal oxides, such as zinc oxide and tin oxide, as well as bariumsulfate, zinc sulfate, calcium carbonate, barium carbonate, clay,tungsten, tungsten carbide, an array of silicas, and mixtures thereof.Fillers may also include various foaming agents or blowing agents whichmay be readily selected by one of ordinary skill in the art. Foamedpolymer blends may be formed by blending ceramic or glass microsphereswith polymer material. Polymeric, ceramic, metal, and glass microspheresmay be solid or hollow, and filled or unfilled. Fillers are typicallyalso added to one or more portions of the golf ball to modify thedensity thereof to conform to uniform golf ball standards. Fillers mayalso be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

Additional materials conventionally included in golf ball compositionsmay be present in the core that is not formed from high levels ofpre-vulcanized or pre-crosslinked material. These additional materialsinclude, but are not limited to, density-adjusting fillers, coloringagents, reaction enhancers, whitening agents, UV absorbers, hinderedamine light stabilizers, defoaming agents, processing aids, and otherconventional additives. Stabilizers, softening agents, plasticizers,including internal and external plasticizers, impact modifiers, foamingagents, excipients, reinforcing materials and compatibilizers can alsobe added to any composition of the invention. All of these materials,which are well known in the art, are added for their usual purpose intypical amounts.

For example, the fillers discussed above may be added to theconventional materials to affect rheological and mixing properties, thespecific gravity (i.e., density-modifying fillers), the modulus, thetear strength, reinforcement, and the like. Fillers may also be used tomodify the weight of the core, e.g., a lower weight ball is preferredfor a player having a low swing speed.

The golf ball components, particularly those components that do notcontain high levels of pre-vulcanized or pre-crosslinked material of thepresent invention, may be formed using a variety of applicationtechniques such as compression molding, flip molding, injection molding,retractable pin injection molding, reaction injection molding (RIM),liquid injection molding (LIM), casting, vacuum forming, powder coating,flow coating, spin coating, dipping, spraying, and the like. A method offlip molding can be found, for example, in U.S. Pat. No. 6,096,255. Amethod of injection molding using a split vent pin can be found inco-pending U.S. patent application Ser. No. 09/742,435, filed Dec. 22,2000, entitled “Split Vent Pin for Injection Molding.” Examples ofretractable pin injection molding may be found in U.S. Pat. Nos.6,129,881, 6,235,230, and 6,379,138. A method of molding components formulti-layer core golf balls may be found in, for example, U.S. Pat. No.6,290,797. Each of these molding references are incorporated in theirentirety by reference herein. In addition, a chilled chamber, i.e., acooling jacket, such as the one disclosed in U.S. patent applicationSer. No. 09/717,136, filed Nov. 22, 2000, entitled “Method of MakingGolf Balls” may be used to cool the compositions of the invention whencasting, which also allows for a higher loading of catalyst into thesystem.

Conventionally, compression molding and injection molding are applied tothermoplastic materials, whereas RIM, liquid injection molding, andcasting are employed on thermoset materials. These and other manufacturemethods are disclosed in U.S. Pat. Nos. 6,207,784, 5,484,870, and, thedisclosures of which are incorporated herein by reference in theirentirety.

The cores of the invention may be formed by any suitable method known toone of ordinary skill in art. When the cores are formed from a thermosetmaterial, compression molded is a particularly suitable method offorming the core. In a thermoplastic core embodiment, on the other hand,the cores may be injection molded.

Suitable methods include single pass mixing (ingredients are addedsequentially), multi-pass mixing, and the like. The crosslinking agent,and any other optional additives used to modify the characteristics ofthe golf ball center or additional layer(s), may similarly be combinedby any type of mixing. Suitable mixing equipment is well known to one ofordinary skill in the art, and such equipment may include a Banburymixer, a two-roll mill, or a twin screw extruder. Suitable mixing speedsand temperatures are well-known to one of ordinary skill in the art, ormay be readily determined without undue experimentation.

The mixture can be subjected to, e.g., a compression or injectionmolding process, and the molding cycle may have a single step of moldingthe mixture at a single temperature for a fixed-time duration. In oneembodiment, a single-step cure cycle is employed. Although the curingtime depends on the various materials selected, a suitable curing timeis about 5 minutes to about 18 minutes, preferably from about 8 minutesto about 15 minutes, and more preferably from about 10 minutes to about12 minutes. An example of a single step molding cycle, for a mixturethat contains dicumyl peroxide, would hold the polymer mixture at 171°C. (340° F.) for a duration of 15 minutes. An example of a two-stepmolding cycle would be holding the mold at 143° C. (290° F.) for 40minutes, then ramping the mold to 171° C. (340° F.) where it is held fora duration of 20 minutes. One of ordinary skill in the art will bereadily able to adjust the curing time based on the particular materialsused and the discussion herein.

Furthermore, U.S. Pat. Nos. 6,180,040 and 6,180,722 disclose methods ofpreparing dual core golf balls. The entire disclosures of these patentsare hereby incorporated by reference herein.

Intermediate Layer

The invention encompasses the use of high levels of pre-vulcanized orpre-crosslinked material in intermediate layers of a golf ball. Thus inone embodiment, an intermediate layer includes high levels ofpre-vulcanized or pre-crosslinked material that has been re-crosslinkedby HPHTS. In another embodiment, an intermediate layer includes highlevels of a blend of pre-vulcanized or pre-crosslinked material that hasbeen re-crosslinked by HPHTS and one or more conventional intermediatelayer material described below. In this embodiment, the intermediatelayer may be formed by providing high levels of pre-vulcanized orpre-crosslinked material and uncured conventional intermediate layermaterial, and subjecting the blend to HPHTS that will simultaneouslyre-crosslink the pre-vulcanized or pre-crosslinked material and cure theuncured conventional intermediate layer material. The materials used insuch intermediate layers, as well as their method of formation, isdiscussed above.

An “intermediate layer” (also known as inner layer or mantle layer) isdefined herein as a portion of the golf ball that occupies a volumebetween the cover and the core. Such an intermediate layer may bedistinguished from a cover or a core by some difference between the golfball layers, e.g., hardness, compression, thickness, and the like. Anintermediate layer may be used, if desired, with a multilayer cover or amultilayer core, or with both a multilayer cover and a multilayer core.Accordingly, an intermediate layer is also sometimes referred to in theart as an inner cover layer, as an outer core layer or as a mantlelayer, i.e., any layer(s) disposed between the inner core and the outercover of a golf ball, this layer may be incorporated, for example, witha single layer or a multilayer cover, with a one-piece core or amultilayer core, with both a single layer cover and core, or with both amultilayer cover and a multilayer core. As with the core, theintermediate layer may also include a plurality of layers. It will beappreciated that any number or type of intermediate layers may be used,as desired.

When the golf ball of the present invention includes an intermediatelayer, such as an inner cover layer or outer core layer, i.e., anylayer(s) disposed between the inner core and the outer cover of a golfball, the intermediate layer can include at least one cover layer madefrom high levels of pre-vulcanized or pre-crosslinked materials.

In some embodiments where an intermediate layer is not entirely composedof high levels of pre-vulcanized or pre-crosslinked materials,conventional materials known to one of ordinary skill in the art may beused, including thermoplastic and thermosetting materials as discussedbelow.

The conventional intermediate layer can include any materials known toone of ordinary skill in the art including thermoplastic andthermosetting materials. For example, the intermediate layer may alsolikewise include one or more homopolymeric or copolymeric materials,such as:

(1) Vinyl resins, such as those formed by the polymerization of vinylchloride, or by the copolymerization of vinyl chloride with vinylacetate, acrylic esters or vinylidene chloride;

(2) Polyolefins, such as polyethylene, polypropylene, polybutylene andcopolymers such as ethylene methylacrylate, ethylene ethylacrylate,ethylene vinyl acetate, ethylene methacrylic or ethylene acrylic acid orpropylene acrylic acid and copolymers and homopolymers produced using asingle-site catalyst or a metallocene catalyst;

(3) Polyurethanes, such as those prepared from polyols and diisocyanatesor polyisocyanates and those disclosed in U.S. Pat. No. 5,334,673;

(4) Polyureas, such as those disclosed in U.S. Pat. No. 5,484,870;

(5) Polyamides, such as poly(hexamethylene adipamide) and othersprepared from diamines and dibasic acids, as well as those from aminoacids such as poly(caprolactam), and blends of polyamides with SURLYN,polyethylene, ethylene copolymers, ethyl-propylene-non-conjugated dieneterpolymer, and the like;

(6) Acrylic resins and blends of these resins with poly vinyl chloride,elastomers, and the like;

(7) Thermoplastics, such as urethanes; olefinic thermoplastic rubbers,such as blends of polyolefins with ethylene-propylene-non-conjugateddiene terpolymer; block copolymers of styrene and butadiene, isoprene orethylene-butylene rubber; or copoly(ether-amide), such as PEBAX, sold byAtofina Chemicals, Inc. of King of Prussia, Pa.;

(8) Polyphenylene oxide resins or blends of polyphenylene oxide withhigh impact polystyrene as sold under the trademark NORYL by GeneralElectric Company of Pittsfield, Mass.;

(9) Thermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers sold under the trademarks HYTREL by E.I. DuPont deNemours & Co. of Wilmington, Del., and LOMOD by General Electric Companyof Pittsfield, Mass.;

(10) Blends and alloys, including polycarbonate with acrylonitrilebutadiene styrene, polybutylene terephthalate, polyethyleneterephthalate, styrene maleic anhydride, polyethylene, elastomers, andthe like, and polyvinyl chloride with acrylonitrile butadiene styrene orethylene vinyl acetate or other elastomers; and

(11) Blends of thermoplastic rubbers with polyethylene, propylene,polyacetal, nylon, polyesters, cellulose esters, and the like.

The intermediate layer also may include ionomeric materials, such asionic copolymers of ethylene and an unsaturated monocarboxylic acid,which are available under the trademark SURLYN® of E.I. DuPont deNemours & Co., of Wilmington, Del., or IOTEK® or ESCOR® of Exxon. Theseare copolymers or terpolymers of ethylene and methacrylic acid oracrylic acid totally or partially neutralized, i.e., from about 1 toabout 100 percent, with salts of zinc, sodium, lithium, magnesium,potassium, calcium, manganese, nickel or the like. The carboxylic acidgroups may also include methacrylic, crotonic, maleic, fumaric oritaconic acid. The salts are the reaction product of an olefin havingfrom 2 to 10 carbon atoms and an unsaturated monocarboxylic acid having3 to 8 carbon atoms.

The intermediate layer may also include at least one ionomer, such asacid-containing ethylene copolymer ionomers, including E/X/Y terpolymerswhere E is ethylene, X is an acrylate or methacrylate-based softeningcomonomer present in about 0 to 50 eight percent and Y is acrylic ormethacrylic acid present in about 5 to 35 weight percent.

The ionomer also may include so-called “low acid” and “high acid”ionomers, as well as blends thereof. In general, ionic copolymersincluding up to about 15 percent acid are considered “low acid”ionomers, while those including greater than about 15 percent acid areconsidered “high acid” ionomers.

Thermoplastic polymer components, such as copolyetheresters (e.g.,HYTREL®, available from DuPont), copolyesteresters, copolyetheramides(e.g., PEBAX®, available from Atofina Chemicals, Inc.) elastomericpolyolefins, styrene diene block copolymers and their hydrogenatedderivatives (e.g. block copolymers of styrene-butadiene-styrene,styrene-(ethylene-propylene)-styren orstyrene-(ethylene-butylene)-styrene, as well as KRATON D®, KRATON G®,KRATON FG® from Shell Chemical), copolyesteramides, thermoplasticpolyurethanes, such as copolyetherurethanes, copolyesterurethanes,copolyureaurethanes, epoxy-based polyurethanes, polycaprolactone-basedpolyurethanes, polyureas, and polycarbonate-based polyurethanes fillers,and other ingredients, if included, can be blended in either before,during, or after the acid moieties are neutralized, thermoplasticpolyurethanes. Examples of these materials are disclosed in U.S. patentapplication Publication Nos. 2001/0018375 and 2001/0019971, which areincorporated herein by reference in their entirety.

The ionomer compositions may also include at least one graftedmetallocene catalyzed polymer. Blends of this embodiment may includeabout 1 pph to about 100 pph of at least one grafted metallocenecatalyzed polymer and about 99 pph to 0 pph of at least one ionomer.Where the layer is foamed, the grafted metallocene catalyzed polymerblends may be foamed during molding by any conventional foaming orblowing agent. In addition, polyamides may also be blended withionomers.

The intermediate layer may also include at least one primarily or fullynon-ionomeric thermoplastic material. Suitable non-ionomeric materialsinclude polyamides and polyamide blends, grafted and non-graftedmetallocene catalyzed polyolefins or polyamides, polyamide/ionomerblends, polyamide/nonionomer blends, polyphenylene ether/ionomer blends,and mixtures thereof Examples of grafted and non-grafted metallocenecatalyzed polyolefins or polyamides, polyamide/ionomer blends,polyamide/nonionomer blends are disclosed in co-pending U.S. patentapplication Ser. No. 10/138,304, filed May 6, 2002, entitled “Golf BallIncorporating Grafted Metallocene Catalyzed Polymer Blends,” the entiredisclosure of which is incorporated by reference herein.

Polyamide homopolymers, such as polyamide 6,18 and polyamide 6,36 may beused alone, or in combination with other polyamide homopolymers. Inanother embodiment, polyamide copolymers, such as polyamide 6,10/6,36,are used alone, or in combination with other polyamide homopolymers orcopolymers. Other examples of suitable polyamide homopolymers andcopolymers include polyamide polyamide 4, polyamide 6, polyamide 7,polyamide 11, polyamide 12 (manufactured as Rilsan AMNO by AtofinaChemicals, Inc. of King of Prussia, Pa.), polyamide 13, polyamide 4,6,polyamide 6,6, polyamide 6,9, polyamide 6,10, polyamide 6,12, polyamide6,36, polyamide 12,12, polyamide 13,13, polyamide 6/6,6, polyamide6,6/6,10, polyamide 6/6,T wherein T represents terephthalic acid,polyamide 6/6,6/6,10, polyamide 6,10/6,36, polyamide 66,6,18, polyamide66,6,36, polyamide 6/6,18, polyamide 6/6,36, polyamide 6/6,10/6,18,polyamide 6/6,10/6,36, polyamide 6,10/6,18, polyamide 6,12/6,18,polyamide 6,12/6,36, polyamide 6/66/6,18, polyamide 6/66/6,36, polyamide66/6,10/6,18, polyamide 66/6,10/6,36, polyamide 6/6,12/6,18, polyamide6/6,12/6,36, and mixtures thereof.

Nonionomers suitable for blending with the polyamide include, but arenot limited to, block copoly(ester) copolymers, block copoly(amide)copolymers, block copoly(urethane) copolymers, styrene-based blockcopolymers, thermoplastic and elastomer blends wherein the elastomer isnot vulcanized (TEB), and thermoplastic and elastomer or rubber blendswherein the elastomer is dynamically vulcanized (TED). Other nonionomerssuitable for blending with polyamide to form an intermediate layercomposition include, but are not limited to, polycarbonate,polyphenylene oxide, imidized, amino group containing polymers, highimpact polystyrene (HIPS), polyether ketone, polysulfone, poly(phenylenesulfide), reinforced engineering plastics,acrylic-styrene-acrylonitrile, poly(tetrafluoroethylene), poly(butylacrylate), poly(4-cyanobutyl acrylate), poly(2-ethylbutyl acrylate),poly(heptyl acrylate), poly(2-methylbutyl acrylate), poly(3-methylbutylacrylate), poly(N-octadecylacrylamide), poly(octadecyl methacrylate),poly(4-dodecylstyrene), poly(4-tetradecylstyrene), poly(ethylene oxide),poly(oxymethylene), poly(silazane), poly(furan tetracarboxylic aciddiimide), poly(acrylonitrile), poly(methylstyrene), as well as theclasses of polymers to which they belong and their copolymers, includingfunctional comonomers, and blends thereof.

The intermediate layer may include a resilient polymer component, whichis preferably used as the majority polymer in the intermediate layer toimpart resilience in the cured state, and a reinforcing polymercomponent as a blend.

Resilient polymers suitable for use in the intermediate layer includepolybutadiene, polyisoprene, styrene-butadiene, styrene-propylene-dienerubber, ethylene-propylene-diene (EPDM), mixtures thereof, and the like,preferably having a high molecular weight of at least about 50,000 toabout 1,000,000.

The reinforcing polymer component preferably has a glass transitiontemperature (T_(G)) sufficiently low to permit mixing without initiatingcrosslinking, preferably between about 35° C. to 120° C. In addition,the reinforcing polymer component preferably has a sufficiently lowviscosity at the mixing temperature when mixed with the resilientpolymer component to permit proper mixing of the two polymer components.The weight of the reinforcing polymer relative to the total compositionfor forming the intermediate layer generally ranges from about 5 to 25weight percent, preferably about 10 to 20 weight percent.

Examples of polymers suitable for use in the reinforcing polymercomponent include: trans-polyisoprene, block copolymer ether/ester,acrylic polyol, polyethylene, polyethylene copolymer, 1,2-polybutadiene(syndiotactic), ethylene-vinyl acetate copolymer,trans-polycyclooctenenamer, trans-isomer polybutadiene, and mixturesthereof. Particularly suitable reinforcing polymers include: HYTREL3078, a block copolymer ether/ester commercially available from DuPontof Wilmington, Del.; a trans-isomer polybutadiene, such as FUREN 88obtained from Asahi Chemicals of Yako, Kawasakiku, Kawasakishi, Japan;KURRARAY TP251, a trans-polyisoprene commercially available fromKURRARAY CO.; LEVAPREN 700HV, an ethylene-vinyl acetate copolymercommercially available from Bayer-Rubber Division, Akron, Ohio; andVESTENAMER 8012, a trans-polycyclooctenenamer commercially availablefrom Huls America Inc. of Tallmadge, Ohio. Some suitable reinforcingpolymer components are listed in Table 1 below with their crystallinemelt temperature (T_(C)) and/or T_(G).

Another polymer particularly suitable for use in the reinforcing polymercomponent is a rigidifying polybutadiene component, which typicallyincludes at least about 80 percent trans-isomer content with theremainder being cis-isomer 1,4-polybutadiene and vinyl-isomer1,2-polybutadiene. Thus, it may be referred to herein as a “hightrans-isomer polybutadiene” or a “rigidifying polybutadiene” todistinguish it from the cis-isomer polybutadienes or polybutadieneshaving a low trans-isomer content, i.e., typically below 80 percent,used to form the golf ball cores of the invention. The vinyl-content ofthe rigidifying polybutadiene component is preferably present in no morethan about 15 percent, preferably less than about 10 percent, morepreferably less than about 5 percent, and most preferably less thanabout 3 percent of the polybutadiene isomers.

The rigidifying polybutadiene component, when used in a golf ball of theinvention, preferably has a polydispersity of no greater than about 4,preferably no greater than about 3, and more preferably no greater thanabout 2.5. The polydispersity, or PDI, is a ratio of the molecularweight average (M_(w)) over the molecular number average (M_(n)) of apolymer.

In addition, the rigidifying polybutadiene component, when used in agolf ball of the invention, typically has a high absolute molecularweight average, defined as being at least about 100,000, preferably fromabout 200,000 to about 1,000,000. In one embodiment, the absolutemolecular weight average is from about 230,000 to about 750,000. Inanother embodiment, the molecular weight is about 275,000 to about700,000. In any embodiment where the vinyl-content is present in greaterthan about 10 percent, the absolute molecular weight average ispreferably greater than about 200,000.

When trans-polyisoprene or high trans-isomer polybutadiene is includedin the reinforcing polymer component, it may be present in an amount ofabout 10 to about 40 weight percent, preferably about 15 to about 30weight percent, more preferably about 15 to no more than about 25 weightpercent of the polymer blend, i.e., the resilient and reinforcingpolymer components.

The same crosslinking agents mentioned above with regard to the core maybe used in this embodiment to achieve the desired elastic modulus forthe resilient polymer-reinforcing polymer blend. In one embodiment, thecrosslinking agent is added in an amount from about 1 to about 50 pph ofthe polymer blend, preferably about 20 to about 45 pph, and morepreferably about 30 to about 40 pph, of the polymer blend.

The resilient polymer component, reinforcing polymer component,free-radical initiator, and any other materials used in forming anintermediate layer of a golf ball core in accordance with invention maybe combined by any type of mixing known to one of ordinary skill in theart.

The intermediate layer may also be a tensioned elastomeric materialwound around a solid, semi-solid, hollow, fluid-filled, or powder-filledcenter. A wound layer may be described as a core layer or anintermediate layer for the purposes of the invention. As an example, thegolf ball may include a core layer, a tensioned elastomeric layer woundthereon, and a cover layer. The tensioned elastomeric material may beformed of any suitable material known to one of ordinary skill in theart.

In one embodiment, the tensioned elastomeric layer is a high tensilefilament having a tensile modulus of about 10,000 kpsi or greater, asdisclosed in co-pending U.S. patent application Ser. No. 09/842,829,filed Apr. 27, 2001, entitled “All Rubber Golf Ball with Hoop-StressLayer,” the entire disclosure of which is incorporated by referenceherein. In another embodiment, the tensioned elastomeric layer is coatedwith a binding material that will adhere to the core and itself whenactivated, causing the strands of the tensioned elastomeric layer toswell and increase the cross-sectional area of the layer by at leastabout 5 percent. An example of such a golf ball construction is providedin co-pending U.S. patent application Ser. No. 09/841,910, the entiredisclosure of which is incorporated by reference herein.

The intermediate layer may also be formed of a binding material and aninterstitial material distributed in the binding material, wherein theeffective material properties of the intermediate layer are uniquelydifferent for applied forces normal to the surface of the ball fromapplied forces tangential to the surface of the ball. Examples of thistype of intermediate layer are disclosed in U.S. patent application Ser.No. 10/028,826, filed Dec. 28, 2001, entitled, “Golf Ball with aRadially Oriented Transversely Isotropic Layer and Manufacture of Same,”the entire disclosure of which is incorporated by reference herein. Inone embodiment of the present invention, the interstitial material mayextend from the intermediate layer into the core. In an alternativeembodiment, the interstitial material can also be embedded in the cover,or be in contact with the inner surface of the cover, or be embeddedonly in the cover.

At least one intermediate layer may also be a moisture barrier layer,such as the ones described in U.S. Pat. No. 5,820,488, which isincorporated by reference herein. Any suitable film-forming materialhaving a lower water vapor transmission rate than the other layersbetween the core and the outer surface of the ball, i.e., cover, primer,and clear coat. Examples include, but are not limited to polyvinylidenechloride, vermiculite, and a reaction product with fluorine gas. In oneembodiment, the moisture barrier layer has a water vapor transmissionrate that is sufficiently low to reduce the loss of CoR of the golf ballby at least 5 percent if the ball is stored at 100° F. and 70 percentrelative humidity for six weeks as compared to the loss in CoR of a golfball that does not include the moisture barrier, has the same type ofcore and cover, and is stored under substantially identical conditions.

Additional materials may be included in the intermediate layercompositions outlined above. For example, catalysts, coloring agents,optical brighteners, crosslinking agents, whitening agents such as TiO₂and ZnO, UV absorbers, hindered amine light stabilizers, defoamingagents, processing aids, surfactants, and other conventional additivesmay be added to the intermediates. In addition, antioxidants,stabilizers, softening agents, plasticizers, including internal andexternal plasticizers, impact modifiers, foaming agents,density-adjusting fillers, reinforcing materials, and compatibilizersmay also be added to any of the intermediate layer compositions. One ofordinary skill in the art should be aware of the requisite amount foreach type of additive to realize the benefits of that particularadditive.

The intermediate layer, may be formed from using any suitable methodknown to one of ordinary skill in the art, particularly for intermediatelayers that do not include high levels of pre-vulcanized orpre-crosslinked material. For example, an intermediate layer may beformed by blow molding and covered with a dimpled cover layer formed byinjection molding, compression molding, casting, vacuum forming, powdercoating, and the like.

For example, castable reactive liquid materials may be applied over theinner ball using a variety of application techniques such as spraying,compression molding, dipping, spin coating, or flow coating methods thatare well known in the art. In one embodiment, the castable reactivematerial is formed over the core using a combination of casting andcompression molding. Conventionally, compression molding and injectionmolding are applied to thermoplastic cover materials, whereas RIM,liquid injection molding, and casting are utilized on thermoset covertechniques.

Cover

The present invention encompasses the use of high levels ofpre-vulcanized or pre-crosslinked materials in the cover or cover layersof a golf ball. Thus in one embodiment, a cover includes high levels ofpre-vulcanized or pre-crosslinked material that has been re-crosslinkedby HPHTS. In another embodiment, the cover includes high levels of ablend of pre-vulcanized or pre-crosslinked material that has beenre-crosslinked by HPHTS and one or more conventional cover materialsdescribed below. In this embodiment, the cover may be formed byproviding high levels of pre-vulcanized or pre-crosslinked material anduncured conventional cover material, and subjecting the blend to HPHTSthat will simultaneously re-crosslink the pre-vulcanized orpre-crosslinked material and cure the uncured conventional covermaterial. The materials used in such cover and cover layers, as well astheir method of formation, is discussed above.

The cover provides the interface between the ball and a club. Propertiesthat are desirable for the cover are good moldability, high abrasionresistance, high tear strength, high resilience, and good mold release,among others.

As used herein, the term “cover” means the outermost portion of a golfball. A cover typically includes at least one layer and may containindentations such as dimples and/or ridges. Paints and/or laminates aretypically disposed about the cover to protect the golf ball during usethereof.

Prior to forming the cover layer, the inner ball, i.e., the core and anyintermediate layers disposed thereon, may be surface treated to increasethe adhesion between the outer surface of the inner ball and the cover.Examples of such surface treatment may include mechanically orchemically abrading the outer surface of the subassembly. Additionally,the inner ball may be subjected to corona discharge or plasma treatmentprior to forming the cover around it. Other layers of the ball, e.g.,the core, also may be surface treated. Examples of these and othersurface treatment techniques can be found in U.S. Pat. No. 6,315,915,the entirety of which is incorporated by reference herein.

In some embodiments where one or more cover layer is not entirelycomposed of high levels of pre-vulcanized or pre-crosslinked materials,conventional cover materials known to one of ordinary skill in the artmay be used, as discussed below.

For example, the cover can include any suitable cover or cover layermaterials, known to one of ordinary skill in the art, includingthermoplastic and thermosetting materials, but preferably the cover orcover layer can include any suitable materials, such as ionic copolymersof ethylene and an unsaturated monocarboxylic acid which are availableunder the trademark SURLYN of E. I. DuPont de Nemours & Co., ofWilmington, Del., or IOTEK or ESCOR of Exxon. These are copolymers orterpolymers of ethylene and methacrylic acid or acrylic acid partiallyneutralized with salts of zinc, sodium, lithium, magnesium, potassium,calcium, manganese, nickel or the like, in which the salts are thereaction product of an olefin having from 2 to 8 carbon atoms and anunsaturated monocarboxylic acid having 3 to 8 carbon atoms. Thecarboxylic acid groups of the copolymer may be totally or partiallyneutralized and might include methacrylic, crotonic, maleic, fumaric oritaconic acid.

This golf ball can likewise include one or more homopolymeric orcopolymeric cover or cover layer materials, such as:

(1) Vinyl resins, such as those formed by the polymerization of vinylchloride, or by the copolymerization of vinyl chloride with vinylacetate, acrylic esters or vinylidene chloride;

(2) Polyolefins, such as polyethylene, polypropylene, polybutylene andcopolymers such as ethylene methylacrylate, ethylene ethylacrylate,ethylene vinyl acetate, ethylene methacrylic or ethylene acrylic acid orpropylene acrylic acid and copolymers and homopolymers produced using asingle-site catalyst;

(3) Polyurethanes, such as those prepared from polyols and diisocyanatesor polyisocyanates and those disclosed in U.S. Pat. No. 5,334,673;

(4) Polyureas, such as those disclosed in U.S. Pat. No. 5,484,870;

(5) Polyamides, such as poly(hexamethylene adipamide) and othersprepared from diamines and dibasic acids, as well as those from aminoacids such as poly(caprolactam), and blends of polyamides with SURLYN,polyethylene, ethylene copolymers, ethyl-propylene-non-conjugated dieneterpolymer, and the like;

(6) Acrylic resins and blends of these resins with poly vinyl chloride,elastomers, and the like;

(7) Thermoplastics, such as urethanes; olefinic thermoplastic rubbers,such as blends of polyolefins with ethylene-propylene-non-conjugateddiene terpolymer; block copolymers of styrene and butadiene, isoprene orethylene-butylene rubber; or copoly(ether-amide), such as PEBAX, sold byAtofina Chemicals, Inc. of King of Prussia, Pa.;

(8) Polyphenylene oxide resins or blends of polyphenylene oxide withhigh impact polystyrene as sold under the trademark NORYL by GeneralElectric Company of Pittsfield, Mass.;

(9) Thermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers sold under the trademarks HYTREL by E. I. DuPont deNemours & Co. of Wilmington, Del., and LOMOD by General Electric Companyof Pittsfield, Mass.;

(10) Blends and alloys, including polycarbonate with acrylonitrilebutadiene styrene, polybutylene terephthalate, polyethyleneterephthalate, styrene maleic anhydride, polyethylene, elastomers, andthe like, and polyvinyl chloride with acrylonitrile butadiene styrene orethylene vinyl acetate or other elastomers; and

(11) Blends of thermoplastic rubbers with polyethylene, propylene,polyacetal, nylon, polyesters, cellulose esters, and the like.

Preferably, the cover includes polymers, such as ethylene, propylene,butene-1 or hexane-1 based homopolymers or copolymers includingfunctional monomers, such as acrylic and methacrylic acid and fully orpartially neutralized ionomer resins and their blends, methyl acrylate,methyl methacrylate homopolymers and copolymers, imidized, amino groupcontaining polymers, polycarbonate, reinforced polyamides, polyphenyleneoxide, high impact polystyrene, polyether ketone, polysulfone,poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethelyne vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers, and blends thereof. Suitable cover compositions also includea polyether or polyester thermoplastic urethane, a thermosetpolyurethane, a low modulus ionomer, such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present inabout 0 to 50 weight percent and Y is acrylic or methacrylic acidpresent in about 5 to 35 weight percent. More preferably, in a low spinrate embodiment designed for maximum distance, the acrylic ormethacrylic acid is present in about 15 to 35 weight percent, making theionomer a high modulus ionomer. In a high spin embodiment, the coverincludes an ionomer where an acid is present in about 10 to 15 weightpercent and includes a softening comonomer.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics and durability. The cover of the golf ballstypically has a thickness of at least about 0.03 inches, preferably 0.03to 0.125 inches, and more preferably from about 0.05 to 0.1 inches. Thegolf balls also typically have at least about 60 percent dimplecoverage, preferably at least about 70 percent dimple coverage, of thesurface area of the cover.

Typically, the covers are formed around the solid or wound cores byeither compression molding preformed half-shells of the cover stockmaterial or by injection molding the cover stock about the core.Half-shells are made by injection molding a cover stock into aconventional half-shell mold in a conventional manner. The preferredmethod is compression molding of preformed half-shells

The cover may include a plurality of layers, e.g., an inner cover layerdisposed about a golf ball center and an outer cover layer formedthereon. For example, the present invention encompasses a golf ballhaving a core, a thin inner cover layer, and a thin outer cover layerdisposed thereon. For example, the core may be formed of are-crosslinked product of the present invention, the inner cover layerformed of an ionomer blend, and the outer cover layer formed of apolyurea composition. In another embodiment, the outer cover layer has adifferent hardness than the inner cover layer.

While hardness gradients are typically used in a golf ball to achievecertain characteristics, the present invention also contemplates thecompositions of the invention being used in a golf ball with multiplecover layers having essentially the same hardness, wherein at least oneof the layers has been modified in some way to alter a property thataffects the performance of the ball. Such ball constructions aredisclosed in co-pending U.S. patent application Ser. No. 10/167,744,filed Jun. 13, 2002, entitled “Golf Ball with Multiple Cover Layers,”the entire disclosure of which is incorporated by reference herein.

In one such embodiment, both covers layers can be formed of the samematerial and have essentially the same hardness, but the layers aredesigned to have different coefficient of friction values. In anotherembodiment, the compositions of the invention are used in a golf ballwith multiple cover layers having essentially the same hardness, butdifferent rheological properties under high deformation. Another aspectof this embodiment relates to a golf ball with multiple cover layershaving essentially the same hardness, but different thicknesses tosimulate a soft outer cover over hard inner cover ball.

In another aspect of this concept, the cover layers of a golf ball haveessentially the same hardness, but different properties at high or lowtemperatures as compared to ambient temperatures. In particular, thisaspect of the invention is directed to a golf ball having multiple coverlayers wherein the outer cover layer composition has a lower flexuralmodulus at reduced temperatures than the inner cover layer, while thelayers retain the same hardness at ambient and reduced temperatures,which results in a simulated soft outer cover layer over a hard innercover layer feel. For example, certain polyureas may have a much morestable flexural modulus at different temperatures than ionomer resinsand thus, could be used to make an effectively “softer” layer at lowertemperatures than at ambient or elevated temperatures.

Yet another aspect of this concept relates to a golf ball with multiplecover layers having essentially the same hardness, but differentproperties under wet conditions as compared to dry conditions.Wettability of a golf ball layer may be affected by surface roughness,chemical heterogeneity, molecular orientation, swelling, and interfacialtensions, among others. Thus, non-destructive surface treatments of agolf ball layer may aid in increasing the hydrophilicity of a layer,while highly polishing or smoothing the surface of a golf ball layer maydecrease wettability. U.S. Pat. Nos. 5,403,453 and 5,456,972 disclosemethods of surface treating polymer materials to affect the wettability,the entire disclosures of which are incorporated by reference herein. Inaddition, plasma etching, corona treating, and flame treating may beuseful surface treatments to alter the wettability to desiredconditions. Wetting agents may also be added to the golf ball layercomposition to modify the surface tension of the layer.

Thus, the differences in wettability of the cover layers according tothe invention may be measured by a difference in contact angle. Thecontact angles for a layer may be from about 1° (low wettability) toabout 180° (very high wettability). In one embodiment, the cover layershave contact angles that vary by about 1° or greater. In anotherembodiment, the contact angles of the cover layers vary by about 3° orgreater. In yet another embodiment, the contact angles of the coverlayers vary by about 5° or greater.

Other non-limiting examples of suitable types of ball constructions thatmay be used with the present invention include those described in U.S.Pat. Nos. 6,056,842, 5,688,191, 5,713,801, 5,803,831, 5,885,172,5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, as well as inPublication Nos. US2001/0009310A1, US2002/0025862, and US2002/0028885.The entire disclosures of these patents and published patent

The convention cover or cover layer material may be applied over aninner ball using a variety of application techniques such as spraying,compression molding, dipping, spin coating, or flow coating methods thatare well known in the art. In one embodiment, the conventional cover orcover layer material is used to form a cover over the core using acombination of casting and compression molding. Conventionally,compression molding and injection molding are applied to thermoplasticcover materials, whereas RIM, liquid injection molding, and casting areemployed on thermoset cover materials.

U.S. Pat. No. 5,733,428, the entire disclosure of which is incorporatedby reference herein, discloses a useful method for forming apolyurethane cover on a golf ball core.

For example, once the conventional cover or cover layer material ismixed, an exothermic reaction commences and continues until the materialis solidified around the core. It is important that the viscosity bemeasured over time, so that the subsequent steps of filling each moldhalf, introducing the core into one half and closing the mold can beproperly timed for accomplishing centering of the core cover halvesfusion and achieving overall uniformity. A suitable viscosity range ofthe curing mix for introducing cores into the mold halves is determinedto be approximately between about 2,000 cP and about 30,000 cP, with thepreferred range of about 8,000 cP to about 15,000 cP.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in a motorized mixer inside a mixing head by feedingthrough lines metered amounts of curative and prepolymer. Top preheatedmold halves are filled and placed in fixture units using centering pinsmoving into apertures in each mold. At a later time, the cavity of abottom mold half, or the cavities of a series of bottom mold halves, isfilled with similar mixture amounts as used for the top mold halves.After the reacting materials have resided in top mold halves for about40 to about 100 seconds, preferably for about 70 to about 80 seconds, acore is lowered at a controlled speed into the gelling reacting mixture.

A ball cup holds the ball core through reduced pressure (or partialvacuum). Upon location of the core in the halves of the mold aftergelling for about 4 to about 12 seconds, the vacuum is released allowingthe core to be released. In one embodiment, the vacuum is releasedallowing the core to be released after about 5 seconds to about 10seconds. The mold halves, with core and solidified cover half thereon,are removed from the centering fixture unit, inverted and mated withsecond mold halves which, at an appropriate time earlier, have had aselected quantity of reacting prepolymer and curing agent introducedtherein to commence gelling.

Similarly, U.S. Pat. No. 5,006,297 and U.S. Pat. No. 5,334,673 both alsodisclose suitable molding techniques that may be utilized to apply thecastable reactive liquids employed in the present invention. However,the method of the invention is not limited to the use of thesetechniques; other methods known to those skilled in the art may also beemployed. For instance, other methods for holding the ball core may beutilized instead of using a partial vacuum.

Dimples

The use of various dimple patterns and profiles provides a relativelyeffective way to modify the aerodynamic characteristics of a golf ball.As such, the manner in which the dimples are arranged on the surface ofthe ball can be by any available method. For instance, the ball may havean icosahedron-based pattern, such as described in U.S. Pat. No.4,560,168, or an octahedral-based dimple patterns as described in U.S.Pat. No. 4,960,281.

In one embodiment of the present invention, the golf ball has anicosahedron dimple pattern that includes 20 triangles made from about362 dimples and, except perhaps for the mold parting line, does not havea great circle that does not intersect any dimples. Each of the largetriangles, preferably, has an odd number of dimples (7) along each sideand the small triangles have an even number of dimples (4) along eachside. To properly pack the dimples, the large triangle has nine moredimples than the small triangle. In another embodiment, the ball hasfive different sizes of dimples in total. The sides of the largetriangle have four different sizes of dimples and the small triangleshave two different sizes of dimples.

In another embodiment of the present invention, the golf ball has anicosahedron dimple pattern with a large triangle including threedifferent dimples and the small triangles having only one diameter ofdimple. In a preferred embodiment, there are 392 dimples and one greatcircle that does not intersect any dimples. In another embodiment, morethan five alternative dimple diameters are used.

In one embodiment of the present invention, the golf ball has anoctahedron dimple pattern including eight triangles made from about 440dimples and three great circles that do not intersect any dimples. Inthe octahedron pattern, the pattern includes a third set of dimplesformed in a smallest triangle inside of and adjacent to the smalltriangle. To properly pack the dimples, the large triangle has nine moredimples than the small triangle and the small triangle has nine moredimples than the smallest triangle. In this embodiment, the ball has sixdifferent dimple diameters distributed over the surface of the ball. Thelarge triangle has five different dimple diameters, the small trianglehas three different dimple diameters and the smallest triangle has twodifferent dimple diameters.

Alternatively, the dimple pattern can be arranged according tophyllotactic patterns, such as described in U.S. Pat. No. 6,338,684,which is incorporated herein in its entirety.

Dimple patterns may also be based on Archimedean patterns including atruncated octahedron, a great rhombcuboctahedron, a truncateddodecahedron, and a great rhombicosidodecahedron, wherein the patternhas a non-linear parting line, as disclosed in U.S. patent applicationSer. No. 10/078,417, which is incorporated by reference herein.

The golf balls of the present invention may also be covered withnon-circular shaped dimples, i.e., amorphous shaped dimples, asdisclosed in U.S. Pat. No. 6,409,615, which is incorporated in itsentirety by reference herein.

Dimple patterns that provide a high percentage of surface coverage arepreferred, and are well known in the art. For example, U.S. Pat. Nos.5,562,552, 5,575,477, 5,957,787, 5,249,804, and 4,925,193 disclosegeometric patterns for positioning dimples on a golf ball. In oneembodiment, the golf balls of the invention have a dimple coverage ofthe surface area of the cover of at least about 60 percent, preferablyat least about 65 percent, and more preferably at least 70 percent orgreater. Dimple patterns having even higher dimple coverage values mayalso be used with the present invention. Thus, the golf balls of thepresent invention may have a dimple coverage of at least about 75percent or greater, about 80 percent or greater, or even about 85percent or greater.

In addition, a tubular lattice pattern, such as the one disclosed inU.S. Pat. No. 6,290,615, which is incorporated by reference in itsentirety herein, may also be used with golf balls of the presentinvention. The golf balls of the present invention may also have aplurality of pyramidal projections disposed on the intermediate layer ofthe ball, as disclosed in U.S. Pat. No. 6,383,092, which is incorporatedin its entirety by reference herein. The plurality of pyramidalprojections on the golf ball may cover between about 20 percent to about80 of the surface of the intermediate layer.

In an alternative embodiment, the golf ball may have a non-planarparting line allowing for some of the plurality of pyramidal projectionsto be disposed about the equator. Such a golf ball may be fabricatedusing a mold as disclosed in co-pending U.S. patent application Ser. No.09/442,845, filed Nov. 18, 1999, entitled “Mold For A Golf Ball,” andwhich is incorporated in its entirety by reference herein. Thisembodiment allows for greater uniformity of the pyramidal projections.

Several additional non-limiting examples of dimple patterns with varyingsizes of dimples are also provided in U.S. Pat. No. 6,358,161 and U.S.Pat. No. 6,213,898, the entire disclosures of which are incorporated byreference herein.

The total number of dimples on the ball, or dimple count, may varydepending on such factors as the dimple size and the selected pattern.In general, the total number of dimples on the ball preferably isbetween about 100 to about 1000 dimples, although one skilled in the artwould recognize that differing dimple counts within this range cansignificantly alter the flight performance of the ball. In oneembodiment, the dimple count is about 380 dimples or greater, but morepreferably is about 400 dimples or greater, and even more preferably isabout 420 dimples or greater. In one embodiment, the dimple count on theball is about 422 dimples. In some cases, it may be desirable to havefewer dimples on the ball. Thus, one embodiment of the present inventionhas a dimple count of about 380 dimples or less, and more preferably isabout 350 dimples or less.

Dimple profiles revolving a catenary curve about its symmetrical axismay increase aerodynamic efficiency, provide a convenient way to alterthe dimples to adjust ball performance without changing the dimplepattern, and result in uniformly increased flight distance for golfersof all swing speeds. Thus, catenary curve dimple profiles, as disclosedin U.S. patent application Ser. No. 09/989,191, filed Nov. 21, 2001,entitled “Golf Ball Dimples with a Catenary Curve Profile,” which isincorporated in its entirety by reference herein, is contemplated foruse with the golf balls of the present invention.

Golf Ball Post-Processing

The golf balls of the present invention may be painted, coated, orsurface treated for further benefits.

For example, golf balls covers frequently contain a fluorescent materialand/or a dye or pigment to achieve the desired color characteristics. Agolf ball of the invention may also be treated with a base resin paintcomposition, however, as disclosed in U.S. patent Publication No.2002/0082358, which includes a 7-triazinylamino-3-phenylcoumarinderivative as the fluorescent whitening agent to provide improvedweather resistance and brightness.

In addition, trademarks or other indicia may be stamped, i.e.,pad-printed, on the outer surface of the ball cover, and the stampedouter surface is then treated with at least one clear coat to give theball a glossy finish and protect the indicia stamped on the cover.

The golf balls of the invention may also be subjected to dyesublimation, wherein at least one golf ball component is subjected to atleast one sublimating ink that migrates at a depth into the outersurface and forms an indicia. The at least one sublimating inkpreferably includes at least one of an azo dye, a nitroarylamine dye, oran anthraquinone dye. U.S. patent application Ser. No. 10/012,538, filedDec. 12, 2001, entitled, “Method of Forming Indicia on a Golf Ball,” theentire disclosure of which is incorporated by reference herein.

Laser marking of a selected surface portion of a golf ball causing thelaser light-irradiated portion to change color is also contemplated foruse with the present invention. U.S. Pat. Nos. 5,248,878 and 6,075,223generally disclose such methods, the entire disclosures of which areincorporated by reference herein. In addition, the golf balls may besubjected to ablation, i.e., directing a beam of laser radiation onto aportion of the cover, irradiating the cover portion, wherein theirradiated cover portion is ablated to form a detectable mark, whereinno significant discoloration of the cover portion results therefrom.Ablation is discussed in U.S. Pat. No. 6,462,303, the entirety of whichis incorporated by reference herein.

Protective and decorative coating materials, as well as methods ofapplying such materials to the surface of a golf ball cover, are wellknown in the golf ball art. Generally, such coating materials includeurethanes, urethane hybrids, epoxies, polyesters and acrylics. Ifdesired, more than one coating layer can be used. The coating layer(s)may be applied by any suitable method known to one of ordinary skill inthe art. In one embodiment, the coating layer(s) is applied to the golfball cover by an in-mold coating process, such as described in U.S. Pat.No. 5,849,168, which is incorporated in its entirety by referenceherein.

Golf Ball Properties

The properties such as hardness, modulus, core diameter, intermediatelayer thickness and cover layer thickness of the golf balls of thepresent invention have been found to effect play characteristics such asspin, initial velocity and feel of the present golf balls. For example,the flexural and/or tensile modulus of the intermediate layer arebelieved to have an effect on the “feel” of the golf balls of thepresent invention.

Component Dimensions

Dimensions of golf ball components, i.e., thickness and diameter, mayvary depending on the desired properties. For the purposes of theinvention, any layer thickness may be employed. Non-limiting examples ofthe various embodiments outlined above are provided here with respect tolayer dimensions.

The present invention relates to golf balls of any size. While “TheRules of Golf” by the USGA dictate specifications that limit the size ofa competition golf ball to more than 1.680 inches in diameter, golfballs of any size can be used for leisure golf play. The preferreddiameter of the golf balls is from about 1.680 inches to about 1.800inches. The more preferred diameter is from about 1.680 inches to about1.760 inches. A diameter of from about 1.680 inches to about 1.740inches is most preferred, however diameters anywhere in the range offrom 1.700 to about 1.950 inches can be used. Preferably, the overalldiameter of the core and all intermediate layers is about 80 percent toabout 98 percent of the overall diameter of the finished ball.

The core may have a diameter ranging from about 0.090 inches to about1.650 inches. In one embodiment, the diameter of the core of the presentinvention is about 1.200 inches to about 1.630 inches. In anotherembodiment, the diameter of the core is about 1.300 inches to about1.600 inches, preferably from about 1.390 inches to about 1.600 inches,and more preferably from about 1.500 inches to about 1.600 inches. Inyet another embodiment, the core has a diameter of about 1.550 inches toabout 1.650 inches.

The core of the golf ball may also be extremely large in relation to therest of the ball. For example, in one embodiment, the core makes upabout 90 percent to about 98 percent of the ball, preferably about 94percent to about 96 percent of the ball. In this embodiment, thediameter of the core is preferably about 1.540 inches or greater,preferably about 1.550 inches or greater. In one embodiment, the corediameter is about 1.590 inches or greater. In another embodiment, thediameter of the core is about 1.640 inches or less.

When the core includes an inner core layer and an outer core layer, theinner core layer is preferably about 0.9 inches or greater and the outercore layer preferably has a thickness of about 0.1 inches or greater. Inone embodiment, the inner core layer has a diameter from about 0.09inches to about 1.2 inches and the outer core layer has a thickness fromabout 0.1 inches to about 0.8 inches. In yet another embodiment, theinner core layer diameter is from about 0.095 inches to about 1.1 inchesand the outer core layer has a thickness of about 0.20 inches to about0.03 inches.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics, and durability. In one embodiment, thecover thickness is from about 0.02 inches to about 0.35 inches. Thecover preferably has a thickness of about 0.02 inches to about 0.12inches, preferably about 0.1 inches or less. When the compositions ofthe invention are used to form the outer cover of a golf ball, the covermay have a thickness of about 0.1 inches or less, preferably about 0.07inches or less. In one embodiment, the outer cover has a thickness fromabout 0.02 inches to about 0.07 inches. In another embodiment, the coverthickness is about 0.05 inches or less, preferably from about 0.02inches to about 0.05 inches. In yet another embodiment, the outer coverlayer is between about 0.02 inches to about 0.045 inches. In stillanother embodiment, the outer cover layer is about 0.025 to about 0.04inches thick. In one embodiment, the outer cover layer is about 0.03inches thick.

In embodiments where the cover, intermediate layer or core layer iscomposed of high levels of pre-vulcanized or pre-crosslinked material, ahemispherical shell is typically formed first. The hemispherical shellgenerally has an outer radius of from about 0.45 inches to about 0.900inches and a thickness from about 0.001 inches to about 0.500 inches.The outer radius and thickness varies depending on whether thehemispherical shell is formed for a cover, intermediate layer or a corelayer, as disclosed herein

The range of thicknesses for an intermediate layer of a golf ball islarge because of the vast possibilities when using an intermediatelayer, i.e., as an outer core layer, an inner cover layer, a woundlayer, a moisture/vapor barrier layer. When used in a golf ball of theinvention, the intermediate layer, or inner cover layer, may have athickness about 0.3 inches or less. In one embodiment, the thickness ofthe intermediate layer is from about 0.002 inches to about 0.1 inches,preferably about 0.01 inches or greater. In one embodiment, thethickness of the intermediate layer is about 0.09 inches or less,preferably about 0.06 inches or less. In another embodiment, theintermediate layer thickness is about 0.05 inches or less, morepreferably about 0.01 inches to about 0.045 inches. In one embodiment,the intermediate layer, thickness is about 0.02 inches to about 0.04inches. In another embodiment, the intermediate layer thickness is fromabout 0.025 inches to about 0.035 inches. In yet another embodiment, thethickness of the intermediate layer is about 0.035 inches thick. Instill another embodiment, the inner cover layer is from about 0.03inches to about 0.035 inches thick. Varying combinations of these rangesof thickness for the intermediate and outer cover layers may be used incombination with other embodiments described herein.

The ratio of the thickness of the intermediate layer to the outer coverlayer is preferably about 10 or less, preferably from about 3 or less.In another embodiment, the ratio of the thickness of the intermediatelayer to the outer cover layer is about 1 or less.

The core and intermediate layer(s) together form an inner ballpreferably having a diameter of about 1.48 inches or greater for a1.68-inch ball. In one embodiment, the inner ball of a 1.68-inch ballhas a diameter of about 1.52 inches or greater. In another embodiment,the inner ball of a 1.68-inch ball has a diameter of about 1.66 inchesor less. In yet another embodiment, a 1.72-inch (or more) ball has aninner ball diameter of about 1.50 inches or greater. In still anotherembodiment, the diameter of the inner ball for a 1.72-inch ball is about1.70 inches or less.

Hardness

The molding process and composition of golf ball portions typicallyresults in a gradient of material properties. Methods employed in theprior art generally exploit hardness to quantify these gradients. Mostgolf balls consist of layers having different hardnesses, e.g., hardnessgradients, to achieve desired performance characteristics. The presentinvention contemplates golf balls having hardness gradients betweenlayers, as well as those golf balls with layers having the samehardness.

It should be understood, especially to one of ordinary skill in the art,that there is a fundamental difference between “material hardness” and“hardness, as measured directly on a golf ball.” Material hardness isdefined by the procedure set forth in ASTM-D2240-00 and generallyinvolves measuring the hardness of a flat “slab” or “button” formed ofthe material of which the hardness is to be measured. Generally,ASTM-D2240-00 requires calibration of durometers, which have scalereadings from 0 to 100. However, readings below 10 or above 90 are notconsidered reliable, as noted in ASTM-D2240-00, and accordingly, all thehardness values herein are within this range. Hardness, when measureddirectly on a golf ball (or other spherical surface) is a completelydifferent measurement and, therefore, results in a different hardnessvalue. This difference results from a number of factors including, butnot limited to, ball construction (i.e., core type, number of coreand/or cover layers, etc.), ball (or sphere) diameter, and the materialcomposition of adjacent layers. Hardness is a qualitative measure ofstatic modulus and does not represent the modulus of the material at thedeformation rates associated with golf ball use, i.e., impact by a club.As is well known to one skilled in the art of polymer science, thetime-temperature superposition principle may be used to emulatealternative deformation rates. For golf ball portions includingpolybutadiene, a 1-Hz oscillation at temperatures between 0° C. and −50°C. are believed to be qualitatively equivalent to golf ball impactrates. Therefore, measurement of loss tangent and dynamic stiffness at0° C. to −50° C. may be used to accurately anticipate golf ballperformance, preferably at temperatures between about −20° C. and −50°C. It should also be understood that the two measurement techniques arenot linearly related and, therefore, one hardness value cannot easily becorrelated to the other.

The pre-vulcanized or pre-crosslinked materials of the present inventionhave a material hardness from about 20 Shore D to about 90 Shore D,preferably from about 20 Shore D to about 80 Shore D, more preferablyfrom about 25 Shore D to about 75 Shore D.

The cores of the present invention may have varying hardnesses, i.e.,surface hardness, depending on the particular golf ball construction, aswell as whether it is formed from high levels of pre-vulcanized orpre-crosslinked materials of the present invention, conventional corematerials or a combination thereof. In one embodiment, the core hardnessis at least about 15 Shore A, preferably about 30 Shore A, as measuredon a formed sphere. In another embodiment, the core has a hardness ofabout 50 Shore A to about 90 Shore D. In yet another embodiment, thehardness of the core is about 80 Shore D or less. In another embodiment,the core has a hardness of about 20 Shore C to about 90 Shore C, andpreferably from about 30 Shore C to about 90 Shore C. In yet anotherembodiment, the core has a hardness of about 20 Shore C to about 80Shore D, preferably from about 20 Shore D to about 70 Shore D.Preferably, the core has a hardness about 30 to about 65 Shore D, andmore preferably, the core has a hardness about 35 to about 60 Shore D.As mentioned above, the upper and lower limits of the ranges disclosedherein are interchangeable to form new ranges. For example, the hardnessof the core may be from about 20 Shore D to about 80 Shore D, or 50Shore A to about 65 Shore D.

The core may have a hardness gradient, i.e., a first hardness at a firstpoint, i.e., at an interior location, and a second hardness at a secondpoint, i.e., at an exterior surface, as measured on a molded sphere. Inone embodiment, the second hardness is at least about 6 percent greaterthan the first hardness, preferably about 10 percent greater than thefirst hardness. In other embodiments, the second hardness is at leastabout 20 percent greater or at least about 30 percent greater, than thefirst hardness.

For example, the interior of the core may have a first hardness of about45 Shore C to about 60 Shore C and the exterior surface of the core mayhave a second hardness of about 65 Shore C to about 75 Shore C. In onegolf ball formulated according to the invention, the first hardness wasabout 51 Shore C and a second hardness was about 71 Shore C, providing ahardness difference of greater than 20 percent.

In one embodiment, however, the core has a substantially uniformhardness throughout. Thus, in this aspect, the first and second hardnesspreferably differ by about 5 percent or less, more preferably about 3percent or less, and even more preferably by about 2 percent or less. Inanother embodiment, the hardness is uniform throughout the component.

The intermediate layer(s) of the present invention may also vary inhardness depending on the specific construction of the ball, as well aswhether it is formed from high levels of pre-vulcanized orpre-crosslinked materials, conventional intermediate layer materials, ora combination thereof. In one embodiment, the hardness of theintermediate layer is about 30 Shore D or greater. In anotherembodiment, the hardness of the intermediate layer is about 90 Shore Dor less, preferably about 80 Shore D or less, and more preferably about70 Shore D or less. In yet another embodiment, the hardness of theintermediate layer is about 40 Shore D or greater, preferably about 50Shore D or greater. In one embodiment, the intermediate layer hardnessis from about 30 Shore D to about 90 Shore D, and preferably from about45 Shore D to about 80 Shore D. In another embodiment, the intermediatelayer hardness is from about 50 Shore D to about 70 Shore D. Theintermediate layer may also be about 65 Shore D or greater.

When the intermediate layer is intended to be harder than the corelayer, the ratio of the intermediate layer hardness to the core hardnesspreferably about 2 or less. In one embodiment, the ratio is about 1.8 orless. In yet another embodiment, the ratio is about 1.3 or less.

As with the core and intermediate layers, the cover hardness may varydepending on the construction and desired characteristics of the golfball. The ratio of cover hardness to inner ball hardness is a primaryvariable used to control the aerodynamics of a ball and, in particular,the spin of a ball. In general, the harder the inner ball, the greaterthe driver spin and the softer the cover, the greater the driver spin.

For example, when the intermediate layer is intended to be the hardestpoint in the ball, e.g., about 50 Shore D to about 75 Shore D, the covermaterial may have a hardness of about 20 Shore D or greater, preferablyabout 25 Shore D or greater, and more preferably about 30 Shore D orgreater, as measured on the slab. In one embodiment, the cover has ahardness of about 20 Shore A to about 70 Shore D. In another embodiment,the cover itself has a hardness from about 30 Shore D to about 60 ShoreD. In one embodiment, the cover has a hardness of about 40 Shore D toabout 65 Shore D. In another embodiment, the cover has a hardness lessthan about 45 Shore D, preferably less than about 40 Shore D, and morepreferably about 25 Shore D to about 40 Shore D. In yet anotherembodiment, the cover hardness is from about 35 to 80 Shore D,preferably from about 45 to 70 Shore D.

In this embodiment when the outer cover layer is softer than theintermediate layer or inner cover layer, the ratio of the Shore Dhardness of the outer cover material to the intermediate layer materialis about 0.8 or less, preferably about 0.75 or less, and more preferablyabout 0.7 or less. In another embodiment, the ratio is about 0.5 orless, preferably about 0.45 or less.

In yet another embodiment, the ratio is about 0.1 or less when the coverand intermediate layer materials have hardnesses that are substantiallythe same. When the hardness differential between the cover layer and theintermediate layer is not intended to be as significant, the cover mayhave a hardness of about 55 Shore D to about 65 Shore D. In thisembodiment, the ratio of the Shore D hardness of the outer cover to theintermediate layer is about 1.0 or less, preferably about 0.9 or less.

The cover hardness may also be defined in terms of Shore C. For example,the cover may have a hardness of about 70 Shore C or greater, preferablyabout 80 Shore C or greater. In another embodiment, the cover has ahardness of about 90 Shore C or less.

In another embodiment, the cover layer is harder than the intermediatelayer. In this design, the ratio of Shore D hardness of the cover layerto the intermediate layer is about 1.33 or less, preferably from about1.14 or less.

When a two-piece ball is constructed, the core may be softer than theouter cover. For example, the core hardness may range from about 30Shore D to about 50 Shore D, and the cover hardness may be from about 50Shore D to about 80 Shore D. In this type of construction, the ratiobetween the cover hardness and the core hardness is preferably about1.75 or less. In another embodiment, the ratio is about 1.55 or less.Depending on the materials, for example, if a composition of theinvention is acid-functionalized wherein the acid groups are at leastpartially neutralized, the hardness ratio of the cover to core ispreferably about 1.25 or less.

Compression

Depending on the desired properties, balls prepared according to theinvention can exhibit substantially the same or higher resilience, orcoefficient of restitution (CoR), with a decrease in compression ormodulus, compared to balls of conventional construction. As used herein,the term “coefficient of restitution” (CoR) is calculated by dividingthe rebound velocity of the golf ball by the incoming velocity when agolf ball is shot out of an air cannon. The CoR testing is conductedover a range of incoming velocities and determined at an inboundvelocity of 125 ft/s. Additionally, balls prepared according to theinvention can also exhibit substantially higher resilience, orcoefficient of restitution (CoR), without an increase in compression,compared to balls of conventional construction. Another measure of thisresilience is the “loss tangent,” or tan δ, which is obtained whenmeasuring the dynamic stiffness of an object. Loss tangent andterminology relating to such dynamic properties is typically describedaccording to ASTM D4092-90. Thus, a lower loss tangent indicates ahigher resiliency, thereby indicating a higher rebound capacity. Lowloss tangent indicates that most of the energy imparted to a golf ballfrom the club is converted to dynamic energy, i.e., launch velocity andresulting longer distance. The rigidity or compressive stiffness of agolf ball may be measured, for example, by the dynamic stiffness. Ahigher dynamic stiffness indicates a higher compressive stiffness. Toproduce golf balls having a desirable compressive stiffness, the dynamicstiffness of the crosslinked material should be less than about 50,000N/m at −50° C. Preferably, the dynamic stiffness should be between about10,000 and 40,000 N/m at −50° C., more preferably, the dynamic stiffnessshould be between about 20,000 and 30,000 N/m at −50° C.

The dynamic stiffness is similar in some ways to dynamic modulus.Dynamic stiffness is dependent on probe geometry as described herein,whereas dynamic modulus is a unique material property, independent ofgeometry. The dynamic stiffness measurement has the unique attribute ofenabling quantitative measurement of dynamic modulus and exactmeasurement of loss tangent at discrete points within a sample article.In the case of this invention, the article is a golf ball core. The golfball material preferably has a loss tangent below about 0.1 at −50° C.,and more preferably below about 0.07 at −50° C.

The resultant golf balls typically have a coefficient of restitution ofabout 0.7 or more. In another embodiment, the ball has a COR of about0.75 or more, and more preferably is about 0.78 or more. In anotherembodiment, the golf ball has a CoR from about 0.7 to about 0.815. Inyet another embodiment, the ball has a CoR of about 0.79 or more, andmore preferably is about 0.8 or more. Additionally, in each of theseembodiments it is also preferred that the COR of the ball is less thanabout 0.819. Alternatively, the maximum COR of the ball is one that doesnot cause the golf ball to exceed initial velocity requirementsestablished by regulating entities such as the USPGA.

The golf balls also typically have an Atti compression (which has beenreferred to as PGA compression in the past) of at least about 40,preferably from about 50 to 120, and more preferably from about 60 to100. As used herein, the term “Atti compression” is defined as thedeflection of an object or material relative to the deflection of acalibrated spring, as measured with an Atti Compression Gauge, that iscommercially available from Atti Engineering Corp. of Union City, N.J.Atti compression is typically used to measure the compression of a golfball and/or a golf ball core. Compression values are dependent on thediameter of the article being measured. The golf ball polybutadienematerial typically has a flexural modulus of from about 500 psi to300,000 psi, preferably from about 2000 to 200,000 psi. The golf ballpolybutadiene material typically has a hardness of at least about 15Shore A, preferably between about 30 Shore A and 80 Shore D, morepreferably between about 50 Shore A and 60 Shore D. The specific gravityis typically greater than about 0.7, preferably greater than about 1,for the golf ball polybutadiene material. The dynamic shear storagemodulus, or storage modulus, of the golf ball polybutadiene material atabout 23° C. is typically at least about 10,000 dyn/cm², preferably fromabout 10⁴–10¹⁰ dyn/cm², more preferably from about 10 ⁶ to 10¹⁰ dyn/cm².

Compression values are dependent on the diameter of the component beingmeasured. The Atti compression of the core, or portion of the core, ofgolf balls prepared according to the invention is preferably less thanabout 80, more preferably less than about 75. In another embodiment, thecore compression is from about 40 to about 80, preferably from about 50to about 70. In yet another embodiment, the core compression ispreferably below about 50, and more preferably below about 25.

In an alternative, low compression embodiment, the core has acompression less than about 20, more preferably less than about 10, andmost preferably, 0. As known to one of ordinary skill in the art,however, the cores generated according to the present invention may bebelow the measurement of the Atti Compression Gauge. In an embodimentwhere the core is hard, the compression may be about 90 or greater. Inone embodiment, the compression of the hard core ranges from about 90 toabout 100.

The core of the present invention may also have a Soft Center DeflectionIndex (SCDI) compression of less than about 160, more preferably,between about 40 and about 160, and most preferably, between about 60and about 120.

Initial Velocity and CoR

The present invention encompasses golf balls that conform and meet withUSGA initial velocity requirements. There is currently no USGA limit onthe CoR of a golf ball, but the initial velocity of the golf ball cannotexceed the current USGA limit of 250±5 feet/second (ft/s). Thus, in oneembodiment, the initial velocity is about 245 ft/s or greater and about255 ft/s or less. In another embodiment, the initial velocity is about250 ft/s or greater. In another embodiment, the initial velocity isabout 253 ft/s to about 254 ft/s. While the current rules on initialvelocity require that golf ball manufacturers stay within the limit, oneof ordinary skill in the art would appreciate that the golf ball of theinvention would readily convert into a golf ball with initial velocityoutside of this range. For golf balls intended for use as practiceballs, the initial velocity may be below 250 ft/s, and even below 240ft/s.

As a result, of the initial velocity limitation set forth by the USGA,the goal is to maximize CoR without violating the 255 ft/s limit. In aone-piece solid golf ball, the CoR will depend on a variety ofcharacteristics of the ball, including its composition and hardness. Fora given composition, CoR will generally increase as hardness isincreased. In a two-piece solid golf ball, e.g., a core and a cover, oneof the purposes of the cover is to produce a gain in CoR over that ofthe core. When the contribution of the core to high CoR is substantial,a lesser contribution is required from the cover. Similarly, when thecover contributes substantially to high CoR of the ball, a lessercontribution is needed from the core.

The present invention encompasses golf balls that have a CoR from about0.7 to about 0.85. In one embodiment, the CoR is about 0.75 or greater,preferably about 0.78 or greater. In another embodiment, the ball has aCoR of about 0.8 or greater.

In addition, the inner ball preferably has a CoR of about 0.780 or more.In one embodiment, the CoR is about 0.790 or greater.

Flexural Modulus

Accordingly, it is preferable that the golf balls of the presentinvention have an intermediate layer with a flexural modulus of about500 psi to about 500,000 psi. More preferably, the flexural modulus ofthe intermediate layer is about 1,000 psi to about 250,000 psi. Mostpreferably, the flexural modulus of the intermediate layer is about2,000 psi to about 200,000 psi.

The flexural modulus of the cover on the golf balls, as measured by ASTMmethod D-6272-98, is typically greater than about 500 psi, and ispreferably from about 500 psi to about 150,000 psi. The flexural moduliof the cover layer is preferably about 2,000 psi or greater, and morepreferably about 5,000 psi or greater. In one embodiment, the flexuralmoduli of the cover is from about 10,000 psi to about 150,000 psi, morepreferably from about 15,000 psi to about 120,000 psi, and mostpreferably from about 18,000 psi to about 110,000 psi. In anotherembodiment, the flexural moduli of the cover layer is about 100,000 psior less, preferably about 80,000 or less, and more preferably about70,000 psi or less. In one embodiment, when the cover layer has ahardness of about 50 Shore D to about 60 Shore D, the cover layerpreferably has a flexural modulus of about 55,000 psi to about 65,000psi.

In one embodiment, the ratio of the flexural modulus of the intermediatelayer to the cover layer is about 0.003 to about 50. In anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.006 to about 4.5. In yet anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.11 to about 4.5.

In one embodiment, the compositions of the invention are used in a golfball with multiple cover layers having essentially the same hardness,but differences in flexural moduli. In this aspect of the invention, thedifference between the flexural moduli of the two cover layers ispreferably about 5,000 psi or less. In another embodiment, thedifference in flexural moduli is about 500 psi or greater. In yetanother embodiment, the difference in the flexural moduli between thetwo cover layers, wherein at least one is reinforced is about 500 psi toabout 10,000 psi, preferably from about 500 psi to about 5,000 psi. Inone embodiment, the difference in flexural moduli between the two coverlayers formed of unreinforced or unmodified materials is about 1,000 psito about 2,500 psi.

Specific Gravity and Shear/Cut Resistance

The specific gravity of a cover or intermediate layer including thecompositions of the invention is preferably at least about 0.7. Inanother embodiment, the specific gravity of a cover or intermediatelayer including the compositions of the invention is at least about 0.6.In yet another embodiment, the specific gravity of the cover orintermediate layer is at last about 1.0, preferably at least about 0.9and more preferably at least about 0.8.

The specific gravity of a core including the compositions of theinvention is greater than 1.5, more preferably greater than 1.8 and morepreferably greater than 2.0. In another embodiment, the specific gravityof the fore including the compositions of the invention is greater than2.5, and can be as high as 5.0 and 10.0.

The cut resistance of a golf ball cover may be determined using a sheartest having a scale from 1 to 9 assessing damage and appearance. Thescale for this shear test is known to one of ordinary skill in the art.In one embodiment, the damage rank is preferably about 3 or less, morepreferably about 2 or less. In another embodiment, the damage rank isabout 1 or less. The appearance rank of a golf ball of the invention ispreferably about 3 or less. In one embodiment, the appearance rank isabout 2 or less, preferably about 1 or less.

Ball Spin

A spin rate of a golf ball refers to the speed it spins on an axis whilein flight, measured in revolutions per minute (“rpm”). Spin generateslift, and accordingly, spin rate directly influences how high the ballflies and how quickly it stops after landing. The golf balls disclosedherein can be tested to determine spin rate by initially establishingtest conditions using suitable control golf balls and golf clubs. Forexample, a spin rate of a golf ball struck by a standard golf driver wasobtained by using test conditions for a Titleist Pinnacle Gold golf ballthat gives a ball speed of about 159 to about 161 miles/hour, a launchangle of about 9.0 degrees to about 10.0 degrees, and a spin rate ofabout 2900 rpm to about 3100 rpm. Thus in one embodiment, the spin rateof a golf ball hit with a golf club driver under the same testconditions is between about 1200 rpm to about 4000 rpm. In a preferredembodiment, the spin rate of a golf ball hit with a golf club driver isbetween about 2000 rpm to about 3500 rpm, more preferably between about2500 and 3000 rpm.

For an 8-iron ball spin test, a spin rate of a golf ball struck by astandard 8-iron club was obtained by using test conditions for aTitleist Pro VI golf ball that gives a ball speed of about 114 to about116 miles/hour, a launch angle of about 18.5 to about 19.5 degrees and aspin rate of about 8100 rpm to about 8300 rpm. Thus in one embodiment,the spin rate of an average, cleanly struck 8-iron shot is between 6500rpm and 10,000 rpm. In preferred embodiment, the spin rate of anaverage, cleanly struck 8-iron shot under the same test conditions isbetween 7500 rpm and 9500 rpm, more preferably between about 8000 rpmand 9000 rpm.

1. A method of manufacturing a golf ball having one or more layerscomprising the steps of: forming at least one layer of the golf ballfrom material comprising a base rubber material and one or morepre-vulcanized or pre-crosslinked materials, wherein the pre-vulcanizedor pre-crosslinked materials comprises greater than about 70 to about200 parts of one or more pre-vulcanized or pre-crosslinked material per100 parts of base rubber material in the layer; and subjecting the atleast one layer to a high pressure, high temperature sintering process.2. The method of claim 1, wherein the golf ball comprises from about 70parts to about 150 parts of one or more pre-vulcanized orpre-crosslinked material per 100 parts of base rubber.
 3. The method ofclaim 1, wherein the golf ball comprises one or more of a core,intermediate layer, and cover, and wherein the pre-vulcanized orpre-crosslinked material is disposed in at least a portion of the core,intermediate layer, cover, or a combination thereof.
 4. The method ofclaim 1, wherein the pre-vulcanized or pre-crosslinked material is athermoset material selected from the group consisting of a thermosetnatural or synthetic rubber, thermoset polyurethane, thermoset polyurea,thermoset polyolefin, thermoset phenol-formaldehyde resin, thermosetamino resin, thermoset furan resin, thermoset unsaturated polyesterresin, thermoset vinyl ester resin, thermoset cyanate esters, thermosetacrylic resins, thermoset epoxy resin, thermoset silicones, thermosetpolyimides, styrene butadiene; polybutadiene; isoprene; polyisoprene;trans-isoprene; ethylene propylenediene rubber; fluoroelastomer;silicone rubber; epoxy rubber; nadimide-, cyanate- ormaleimide-terminated thermosetting polyimides; and mixtures thereof. 5.The method of claim 1, wherein the pre-vulcanized or pre-crosslinkedmaterial further comprises a cis-to-trans catalyst and free radicalsource; a crosslinking agent; a vulcanization accelerator; ananti-reversion agent, or a mixture thereof.
 6. The method of claim 5,wherein the anti-reversion agent is1,3-bis-(citraconimidomethyl)benzene,hexamethylene-1,6-bis(thiosulfate), or a mixture thereof.
 7. The methodof claim 1, wherein the golf ball has an Atti compression of at leastabout
 40. 8. The method of claim 1, wherein the golf ball has acoefficient of restitution of at least about 0.7, and wherein the golfball has an initial velocity of about 245 ft/s or greater.
 9. The methodof claim 1, wherein the golf ball has a coefficient of restitution of atleast about 0.78.
 10. The method of claim 1, wherein the golf ball has aball spin rate of about 1200 rpm to about 4000 rpm when the golf ball ishit with a golf driver.
 11. The method of claim 1, wherein the golf ballhas a ball spin rate of about 6500 rpm to about 10,000 rpm when the golfball is hit with an 8-iron.